All of the above plus........... Remove all the plastics and inspect all the connections in the wiring loom. check the earth block, big red wire coming from the main 30A fuse, look for spliced in zombie wiring and see where it goes. Check the connectors coming from the rectifier. Replace anything that looks burned out or flaky because it will almost certainly let you down soon if you don't. Check the forum for advice.
it's worth having a look at the PCB behind the instrument panel to see what condition it's in. By now some of the tracks may be corroded through and the will cause issues with the displays. There are some straightforward repairs you can do.
Depending on how keen you are, consider replacing rubber hoses, check the thermostat and hosing around that area (it's a pig to get to though). Check out GreginDenver's posts here on the subject and his VFR refresh posts for what is possible. He's got some good advice about perishables!
It will also be worthwhile downloading a copy of the full workshop manual.It's on here somewhere, and a lot better than the Haynes manual.
If you need spares, check out David Silver and M&P. Ebay has a wealth of VFR material too.
Post some photos.