Is there input shaft seal missing? If your manual is like mine there is a circular cork seal they fits over the input shaft and seals the area between the shaft and throw out bearing support. Just a guess on yours. Mine leaked out of the front when the seal gave up.
See the black in color seal around the shaft? Does your have a place for it?
The spring side of the seal goes towards the transmission. In this position it holds the transmission fluid in the transmission. When you reassemble use the guide pins as shown in the manual. I used bolts with the heads cut off. This really helps from buggering up the seal. Had to do a seal over again with being careless with reassembly.
Gulp. Very tough to find/rebuild, etc. There are a lot of threads on this unit and what to look for as possible resolutions to your problem. I think switching over to a vacuum booster requires a lot of modifying.
I'm not sure why you would do this. The starter circuit services other parts of the car. Have you located the fusible link and tested it? The rodent tenants are more then likely the cause of problem. All wiring needs to be checked for chew marks and open wires that are grounding out.
The battery itself could also be the issue. If the link is burned consider replacing the battery and both cables. Check the wires in the circuit for open insulation. Once you have it running again, use a trickle charger for long periods of sitting.