Do I absolutely have to drop the oil pan AND replace the pan gasket to install a new rear main seal housing gasket? The pan gasket has less than 200 miles on it. Can i just pry it out and slide in a new one (like you can for the RMS itself) or am i on crack?

I installed a lower mileage LT1 and did the intake and oil pan gaskets while on the stand. Being new, I didnt bother to install a new RMS and front seals. So leaks galore.

 

You don’t have to replace the gasket every time you drop the pan. Even if it rips just put some quality sealant like Ultra Black or Right Stuff in/on/above/below the cracked gasket, tighten the pan back up and let it cure for a good 24 hours before starting the engine.
the gasket fits into a grove onto the housing. Trying to pry the gasket out/put back in place with the pan still torqued down will most likely damage it.

 

I assume pretty much the whole pan needs to drop enough to get the housing out?

 

Dropping it as in removing all bolts and nuts and letting it rest on the k-member. Should have ample clearance to take the housing out.