Rear main is stupid easy, don't need to yank the retainer at all. There are 3 cuts in the retainer that allow you to pry the seal out and slap another one in. This is what I did with the Camaro last year. As far as a halfass overhaul, I did one on the Camaro back in 2015 but that was a supposed 67k motor before it got dropped in a race car and beat on for God only knows how many seasons. It's still putting the numbers down as I just hit the dyno. Also had the heads off of my 1500 around 230k, slid in new bearings and a marine cam, slapped it back together. As long as there isn't a huge ass ridge or piston knock I'd do it, but I'm just that way. Willing to put a lot of effort into trying to see what I can get away with depending on the circumstances.