Vacuum Pump Rebuild 300TD

[benchracer]

I was getting fluctuating vacuum readings from main vacuum line, dial would creep up to almost 20 Hg before dropping down to under 10, then start creeping up again. Decided I'd take off the pump and have a look. I then removed the front cover, held on by about six or seven screws. I see what looks like 3 one-way plastic valves, I'm sure these should probably be replaced as there is oil in the front half of the pump and I'm guessing it should not be there. I have a question about what else I should be looking for. Under the front cover is a
nut in the center of what looks like might be a piston. However this piece does not seem to move. On the back side, there is a large spring which seems like it is compressed by a lever with a wheel on the end. Do I need to take this lever apart. Seems like it's under spring tension. If so, how do I go about disassembling the rest of the pump. I assume all these parts are a part of the pump rebuild kit I've heard of. I've also heard something about a rubber bladder that tends to disintegrate, but I don't see any rubber bladder. Anyone?