You might want to look at tractorhouse.com, machinefinder.com and fastline.com to get some idea of what prices are.
Tractordata.com is a great site to get tractor specs.
The following site will give part cost and part catalogs. Parts are expensive, sometimes better to pay a little more for a nicer tractor.
https://jdparts.deere.com/servlet/com.deere.u90.jdparts.view.publicservlets.HomeUnsigned
The following site will give you online manuals for 1999 and newer tractors.
John Deere Ag - New Equipment: Technical Publications - Equipment Search
As already suggested what are you looking to accomplish with a tractor?
Tractordata.com is a great site to get tractor specs.
The following site will give part cost and part catalogs. Parts are expensive, sometimes better to pay a little more for a nicer tractor.
https://jdparts.deere.com/servlet/com.deere.u90.jdparts.view.publicservlets.HomeUnsigned
The following site will give you online manuals for 1999 and newer tractors.
John Deere Ag - New Equipment: Technical Publications - Equipment Search
As already suggested what are you looking to accomplish with a tractor?