I can't help you on the A/C stuff...I leave that to the pros!
As far as the DIY gods, they pretty much strike me with lightning bolts every time I tackle a project.
My very first DIY (at 16) was replacing a fuel pump on a VW Beetle...simple enough, pump sits right in front of the engine, easily accessible, two nuts, and two hoses, comes right off. Half hour tops right?
Some how in the process, the plunger jammed into the shaft hole. Upon trying to remove it, shattered the phenolic mount and watched all of the little bitty pieces fall into the crankcase. Boy did I scream that day!
At least my mechanic was resourceful. After I had the car towed to the shop, he just drained the oil, pulled off the oil pump, and reached in the case and picked all of the pieces that didn't come out of the sump plate.
25 years later, I am about 50-50 on "DIY no problemo" to "DIY Homer Simpson scenario".
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car