BWINFLD

I got this bike from my brother got it running after 10yr every thing work except headlight and starter. He told me that it usually come on when running. And the elec starter would only work when he put a new battery. The headlight came on once when i had put the battery charger. I know the bulb is good. I put new batt rides good no headlight. No elec starter. I jump the starter and it work but not with button.

I have a 81 xs400 spII with drum brakes how much trouble to change to disc on the front. I also want to change from spokes to mags. what front forks will interchange easy? Will the mag wheel in the back just bolt on like the spoke rim?