I refurbished the pop bumpers – I replaced all the plastic and electric parts inside and polished the plasic. I am new at this after all, and so I did manage to screw them up pretty well by shorting out a coil by mistake along the way. It took weeks of troubleshooting to figure out. I pored over the service manual and posted in the rec.games.pinball Usenet newsgroup in search of help. If you are interested, that thread can be found here:
Suffice it to say that I replaced a lot of fried system board components to finally get things working. I learned a TON about electronics during this process and in the end I was glad it happened.
I also want to give Kudos to Rob Anthony from RGP who spent a lot of time writing helpful advice in my thread above. I highly recommend him for any of your pinball repair needs! Here is is his information.
Quality Board Work – In Home Service