Reply to "Pantera for the novice?"

Accessing the motor is not that bad. You get to the sides by leaning over, or you can easily climb in and perch on the transaxle if you really need to. You get to the front by removing a couple panels behind the seats, giving you access through that firewall (it's a reasonable opening, maybe 1.5' x 1.5' roughly). You can also (theoretically) easily remove the rear 1/4 windows for easy access to the front upper areas. About the only real challenges would be:
1. Dropping the oil pan, IF stock crossmember underneath hasn't been cut out & replaced with a removable one.
2. Fuel tank issues, requires engine removal. But engine removal is not bad, no worse and probably easier than most other cars.

All those jobs you mention are very do-able with engine in, headers are easy from underneath, intake not too bad, heads not too bad though not that much harder to pull the engine at that point.