It just takes some time and chrome polish to get the "shine" back. As for what can go wrong with the saw? Not much, the pinion gears some times need adjusting to keep the tilt and lift of the trunnion moving smoothly and easily. Typically the magnetic starters are the first thing to really go out, but I've only seen it happen to one saw personally. That was at a shop that had probably 8 Powermatic M66's in it. It was a old saw.
I personally would never purchase a 3hp table saw, except if it were to be used for dadoing alone. I have a 5hp saw Model 66 and occasionally wish it had a bit more oomf.
My saw was purchased new in 2004, it has a Baldor motor. Had it out once for service. I thought a bearing was going out.The search goes on for my PM 66, 3-HP, 1-PH beauty. Does PM experts know when PM stopped using Baldor?
Look for used equipment when you can. There are cabinet shops going tits up all over the place. Craigslist is a good source, as is K-Bid. Two weeks ago there was 3 shops on K-Bid going out of business in my area.