For the exhaust, the muffler will gain you no performance. Only sound. If you want to upgrade to a performance muffler, add a resonator between the muffler and the cat also. The 92/93 didn't get one from the factory, and the exhaust will be raspy and 'pop' without one if you upgrade to a free-flowing muffler at this point. I added a magnaflow resonator to my 93 for the same reason.
For the rockers, if you've never done them, my best advice would be to get help from someone who has. You have to find a way to hold the valves up during the procedure. There are two methods. One is filling the cylinder through the spark plug hole with string, the other is with compressed air.
In either case, you should replace your valve springs and pushrods also at the same time. You need a valvespring compressor (tool) and some patience. You're looking at a total cost of about 500 including various parts and gaskets for this. You SHOULD tear your SC off and replace the LIM gaskets at the same time. Your SC is probably due for a coupler by now as well.
In order to support the flow from a 2.2" pulley and rockers, you MUST remove your Exhaust manifolds, have them stitch-welded on the outside, and ported on the inside. Remove the entire factory weld. Repair all cracks (you have them, trust me) at this time. Also make sure you check your fuel pressure. Your car is in the danger zone for age of the pump, and if you run lean under boost..........BOOM.