Tune up on a Highland Park B-12

With a 10 inch or larger blade oil is better IMO. The problem is it's spraying around everywhere even when you're running the grinder. Water with a good quality additive like Lube cool from Johnson bros or Smokeys EZ cut will keep things from rusting.
To my knowledge HP China only makes compatible replacement parts for slab saws, not really compatible at all unless you don't mind putting yugo parts on a Mercedes. If you contact Cigarbox ask them what they think of the Chinese stuff. Sorry coloradocliff I've had to deal with several extremely perturbed former customers of theirs and decline to attempt to fix their broken crap.

IMPORTANT: If it has the original 10 year old Silicon Carbide grinding wheels be very careful. I had an aluminum oxide wheel fragment nail me in the jaw once. Never stand in front of them and leave them running to spin dry when you shut off the water supply, and as soon as the budget permits replace them with diamond.

coloradocliff first new HP saw I put my hands on was their demo at the pow-wow in q-site a few years back. As I always do with a saw I'm considering I grabbed the top of the vice and wiggled, it was looser than most 50+ year old used saws, the cast parts were pitted, basically a nice coat of paint on a turd. A club member in his 80's is getting the shuck and jive about repairs to his 18" chinese HP with about 10 hours of use before it broke.
I made a saw top out of acrylic once, would definitely contain the spray. Draining when not in use works too. Those units are definitely durable and pretty easy to use, the clubs lapidary shop has a HP combo w/o saw and the only thing I've had to do is replace wheels and a water valve.

I have restored or at least resurrected a saw similar to yours except mine has separate motor for saw and arbor.
Use oil if your shop configuration can tolerate a bit of oil. I can position a plexiglass shield to the left side of the saw blade and one on the right (using an "H" like bracket used in installing shower glass panels (the panels can be moved as needed. Don't trust the antirust of most water additives. They retard but do not prevent rust. JSGems can sell you Nova wheels if that's what you want ,but you probably need an 80 or 100 grit hard wheel and alternatives up from there. I managed to squeeze three wheels in the space originally containing two. If you are going to use that buffer wheel closest to the saw, you should keep it covered to prevent grit contamination. That's the spot where I put my 80 grit wheel.
If your unit is complete you may not need parts other than wheels and ultimately bearings, but if it spins ok at present, I wouldn't touch the bearings (although you may have to remove one of them to replace the wheels.
The belt may just need adjustment or a bit of belt dressing. Again it may be necessary to either remove a bearing or use a segmented belt when it comes time to replace the belt so avoid if you can make do. Its a great machine and should serve you well. Shortcomings are that its not easy to change wheels or accommodate everything you need to finish cabs, but its rock solid and a good start. The saw can be made into a gravity feed, but probably you will hand feed it with or without the vice. I'll add a photo in case you want more info on shielding the spray from the saw.
This is just a rough piece of plexiglass that I move where I need it. The H bracket just clips onto the side of the saw tray.

Plus 1 on nova wheels from "JSGems can sell you Nova wheels"

Peruano what did you have to do to eliminate the buffer wheel and add the 80 grit wheel? Any modifications or did yours come like that?

Count your wheels or potential wheels from left to right. The one closest to the saw is currently a buffer, and housed in a galvanized tank and shield. It probably does not have a water supply or drain but both are easily added. This buffer is held on by a nut and easily replaced with an 8" wheel (80 or 100 grit hard wheel). The bearing is beside that and need not be disturbed to make this addition. The next bay (wheels 2 and 3) is located between the bearing to the left and right. You will need to loosen the entire arbor shaft and remove one of the bearings to slide these wheels off. Its a bit of a challenge but not impossible. The fourth wheel or space on the right of the 2nd bearing is usually occupied in these old machine by what is called thumper wheel. I replaced that with an expand wheel that allows me to substitute belt of various grits as I work toward the final sanding and polish. Your machine seems to be lacking the hood and tray here (as was mine so I bought a hood and tray from Lortone to make this a functional bay. I removed the polishing wheel (flat disc) but can put it back on when needed - it obstructed belt changeouts.
As I mentioned before I managed to squeeze 3 wheels in the space where you currently have 2 silicon carbide wheels. Mine are 280, 600, and 1200 grits.
If you plan on using the saw, I'd consider making a couple of shields that can be moved around depending on where spraying is occurring. If you are sawing pebbles or rounded beach stones you will definitely get spray to the side and a lateral shield will prevent a lot of mess. The problem with daily draining (inherent with water in saw) is that the drain is in the back (not easily accessed) and the top is not that easy to remove from the saw table (necessary to allow drying in there). Hence oil is the way for me. You do need space to get your hands in the saw area but any other area on the side and toward you person can be shielded. A top is not absolutely necessary but one could be advantageous depending on the type of saying done. The amount of lubricant (depth on blade) is obviously a major factor in how much spray and mist you get while sawing. I hope this discourse helps you with your planning and renovation. Enjoy the process.