Have a read through this, http://www.pinrepair.com/sys1/index.htm
It sounds like you have plenty of bugs to iron out and most of the answers will be in that document which is probably the most comprehensive Sys 1 repair guide available.
From memory, you need to use 9V to rejuvenate a Gtb display which can be found at the lock out coil on the door. there is info on this in the Sys 1 pinrepair guide. Doing this will not solve the display issues you have though.
good chance the coils are no good on the chime unit. If the plunger will not travel through them they need replacing. If they are cooked, then the driver board will mor than likely need attention before you replace the coils.
Same thing for the drop target solenoid not working or there is a transistor that will be mounted under the playfield that will probably need replacing. Again, there are details on all of this in the pinrepair guide.