All of the leaks that you mentioned are all very common on that vehicle.

The valve covers are about as easy as you can get to replacing yourself.
the P/S pump may not be something you want to reseal yourself.
You may get lucky and just the resevoir gasket is leaking which is not too bad to regasket.

The rear diff seals get some seepage from them, just keep an eye on the leaks to see if they worsen in time.
For the time being, you could change the diff lube and top it off with new lube, then clean the area real good and keep an eye on the leaks.