Welcome horsin,
Haven't had my MX5000 too long, but really like it so far. Engine seems plenty powerful enough for that size tractor and very smooth. It is a bit of a high-revver though and has to turn 2700 RPM to reach 540 at the PTO. So far I've only done bush hogging, stump pulling and some light loader work with it and, even with the bush hog, have not yet seen any need to go above 2200 RPM. The 8x4 transmission is very easy to use; like it the best of any I have.
Mine came with the extendable 3PH arms. They're a big help in getting hooked up. Loader is strong and the bucket rolls way back. The 4WD is real handy for stump pulling and getting out of trouble.
Check the fluids, look for signs of abuse, start her up, try all the gears, pay attention to clutch engagement, listen for funny sounds (some noise is normal, the tractor has a bull gear final drive), run the pto, see if it steers right, engage 4WD, check brake function, run the 3PH up & down, see if the gages & lights work, see if the radiator screen is clean, and exercise the loader. That should keep you busy for a few minutes....
If you buy it, go over all the loader bolts and wheel lug nuts when you get it home to make sure they're tight. Will it be a private sale or through a dealer? How many hours? Make sure they give you the manuals....you'll need them for servicing instructions.
Bob