> if you are young, fit, have the proper tools to lift and support the car, have an oxy-acetylene torch available and don't mind wiggling around on the ground while wrestling stuck together rusty parts

I am old, have had three joint replacements, and work off of jack stands. I still manage to do the exhaust work on the 7 and 9 series cars on my roster.

I seldom work on individual components but I can if necessary. The starting point to be able to do that is initially replacing everything from the cat back. When assembling the system I slather the contact surfaces with anti-seize and then only tighten the clamps enough to prevent movement.

If it becomes necessary to separate the components it usually isn't too bad. A warm shower and a couple of beers usually brings my body back around from the experience.
--
Any twenty minute job is just a broken bolt away from a three day ordeal