Mike, from the standpoint of a complete novice (me) with a TO-20, the Shop Manual is MUCH more detailed and complete than the I&T Manual. (I have both.)
That said, there are a few pictures and drawings that are actually better in the I&T manual than in the "official" Shop Manual - the print job on the Shop Manual reprint isn"t the best.
I didn"t get the Shop Manual from this site, but I think I paid about the same price that you mentioned.
Check Amazon for the I&T book - I think I got mine for like Nine (9) bucks, shipped.