Updated as of 8 am this morning: an offset box wrench won't work on my 485 DI, the fit between the two bolt heads is just too tight. I eventually DID get the 3/4" bolt loosened (the vertical bolt I describe, from the hydraulic control) and unscrewed it as far as it would go, but it won't come all the way out because of the top tranny cover. It DID come far enough out that it no longer interfered with the 9/16" bolt on the transmission plate, so that suckered me into thinking that I had this thing beat. But.... the 9/16" bolt is too long and will not come out due to interference from the hydraulic control. So the only way to get the top cover off is to follow the instructions in the manual, which are to remove the entire rear (the lift arms, 3 pt setup, hydraulic reservoir) and THEN take that one %$#@ bolt out. Local guy quoted me 10 book hours and the cost of parts, which will end up roughly $800 per his "rough estimate." Joy.
My brother is an auto mechanic, and he is willing to come up next weekend and work on it with me. We might just try to get this thing broken down, though until it's completely disassembled, I won't even know if I can fix the issue (the local guy tells me over the phone that it's likely the counter shaft, and that the reason that 4th didn't work was that it originally had a couple teeth break and then progressed to the point that I lost all my low range). That part lists for over $200.00 alone.
Anyone that's done this kind of stuff before have any input, whether good, bad, or indifferent? Anyone wanna talk me down from the ledge here? Anyone?