Mine's a 1990 1418 with the old 3-pin attach. I'd question the guy about the year again, or just get him to give you the serial#, then call Power-trac, talk to Don Boyd, and find out what year it was built. I'm thinking 1998 sounds a little too new to have the 3 pin deal rather than the current quick-attach, but I could very well be wrong.
I'd suggest that if/when you pick it up, do these things:
1) Examine it in detail. I've replaced quite a few bursted hoses on my old one. It sounds simple (and it really is), but when a hose bursts, you dump a bunch of oil out, and you have to find the burst hose (which isn't always easy), take it off, measure it, order a replacement, and wait, OR, take it off and take it to a Carquest or similar that can make hydraulic hoses, then put it back on, and hope you changed the right one. Hint: unplug the spark plugs and crank the starter when you're looking for a burst hose. That way, you don't get sprayed in the face with high-pressure oil, and you don't dump all the hydraulic oil (and thus burn up the hydrostatic drive pump). When you examine it, look for any fresh oil, run your hand down hoses to feel for sections that have a worn spot, etc.
2) Hook up every attachment that going with it, and try it out. Run this thing hard (and as long as you can) before you hand the person a check, and drive off with it. If you possibly can, get a friend who's a diesel and/or hydraulic mechanic to come with you to check it out. If it's going to break, it'll break after it's heated up and the hydraulic oil pressure is at it's high, and you want it to break before you buy it rather than after you get home with it.
3) When you call PT with the serial#, ask Don for help in what to look for in terms of it's condition. He helped me a lot with my purchase.
All that said, it's a pretty simple machine, and you can probably fix most stuff yourself. I have, with the exception of some engine work that I recently had done. $12K seems like a rather high price to me for a used one, so make sure it's in good enough shape to justify the price. And have fun while you're doing it! If I had paid that much for mine, I'd have expected to have to repair very little!
HTH,
Dave