Hey man heres my advice. I just did the valve cover cover gasket job- real easy with basic tools. Buy the kit from pelicanparts.com or bavauto.com or somewhere, that way you get the exact parts you need. I reused the rubber bolt gaskets (what youre calling the sealing washers) cause they were in OK shape (and i have a 94). If the O2 sensors havent been done in a while, that could be youre problem here on the CEL. You should run some fuel system cleaner through your system and replace the fuel filter (not hard either). Start with the small stuff first and see if that fixes it. Not sure which valve is the purge valve but replace it if you think you can do it yourself.
The power steering system can be bled and refilled easily, buy a manual or search around on how to do it, you dont need to take anything apart. Tighten down any clamps you can or replace them with new ones.
If you are heading off to school, I would get an alignment/ rotation and balance from a good shop especially if you are driving a ways. Tires are expensive and you want to make sure they are well taken care of. Check air pressure too.
Replacing your cats/ exhaust is not cheap...Id do it only if you have to for inspection or if its too loud to stand.
Just be sure to research each issue as much as you can, before you pay some mechanic all your beer money to do a job you can probably do yourself.