Del, I"m a poor one to offer advice (since I"m usually the one asking for it), BUT here"s a link to some Ferguson-specific stuff from the FENA website that may be helpful.
Otherwise, Jason is right about the fluids, and the tire size.
I paid $1,350 last fall in Missouri for a TO-20 that didn"t have any major problems - that"s not quite as much tractor as a TO-30, though.
I saw a "fancied-up" TO-20 sell for around $2,200 in February, but it smoked, the hydraulics were moving slow, and it didn"t run as well as mine.
Finally, I"ve read your posts in the N forum here on YT, as well as the "other" N Board, and I think it"s safe to say that you"ll have a pretty good idea of what you"re looking at!