if you've got splitting stands, rear main seal can be changed in a day.
steering parts are available aftermarket pretty reasonable.
do you need 3 pt? i believe a wheatland can have a 3 pt added, but that is a bigger project.
don't know a 4010 from experience, but that 806 is a darn good tractor.
that being said, it's your farm, you gotta make the call.