I did this before. I was able to tighten the nut with a big crescent wrench and some other wrench. I think I used a pipe wrench. I removed the entire exhaust. I undid the four bolts at the union of the exhaust manifolds and the downpipes and removed all the rubber exhaust hangers. Support the rear of the exhaust on blocks then drop the front. It is a little tricky to get the front lined back up when reassembling but not too bad. While you are in there check the bushing for the shift linkage and the front flex coupling. Not too bad to replace
I have a 91 300e