I personally like the carbed versions a little better, but there are advantages to fuel injection when it's working right. I've heard that 93-94 M900s had a few problems that went away by 95.
Definitely look for service records. If the seller can't prove when the cam belts were changed, valves adjusted, etc., then plan on spending more $$ to make all that stuff fresh.
My personal experience plus similar info gleaned from posts here and elsewhere is that a well maintained Monster coming up on 12,000 miles is probably ready for the following normal wear items very soon: cam belts, valve adjustment, fork oil and brake fluid R&R, chain and sprockets, clutch pack, a few nickle and dime electrical items(read that in large nickels and dimes - $50 & $100), maybe brake pads, and maybe one or both tires depending on how it was ridden.
I couldn't get written records for my bike, but did get to talk to the previous owner who refuted several of the claims made by the shop I bought it from. Since it was coming up on 12K and I had confirmed what hadn't been done I had to spend some more money. But the upside is that I know everything is right because I did it myself. Plus, by doing it all when first getting the bike I'm enjoying the benefits of the money spent rather than playing catch up or maybe spending money later to make the bike saleable (as if I'll ever let this one go!).
Don't be afraid to haggle over upcoming maintenance items and shop around. There are enough good bikes out there - just choose carefully and you will do well.