The area that I would look at is the transmission and what the tractor had been used. If it has a collarshift or syncshuttle it has a dry clutch, if used a fair amount for loader work down the road you could need a new clutch. Big ticket item as the tractor has to be split in half. See how much free play there is in the clutch, less than half inch normally means clutch wear. I have included the URL to the owners manual, shows you how to check the free play. The manual also includes servicing. Make sure the tachometer is working, as hours may not increase if the tach is not working. Make sure the loader can pick up the front of the tractor when lowered, will give you some idea on the hydraulics.
On the price does it have MFWD and what type of transmission? I have included URLs on sites to compare prices.
I have 5210 same tractor less the turbo. I have been very happy with it. Literally my tractor starts with just a flick of the key. Some people express concern on the noise of the engine, I wear ear protectors.
If you decided to purchase it, post back and I will share with you some URLs you may find of interest. You may also what to search this site to see what others have said.
If it does not have MFWD and you are going to be doing a loader work, you may NOT be happy with your purchase. This is NOT a comment on the tractor, just that I feel you need MFWD if you are going to do much loader work.
Manual
http://manuals.deere.com/omview/OMRE71736_19/?tM=
Fastline.com tractor and equipment prices
Machinefinder.com tractor and equipment prices
Tractorhouse.com tractor and equipment prices
Tractordata.com great site to get specs on a tractor