For the Headlight, pull the headlight out & clean the contacts,
then use that 99cent electrical connection goop they sell at the counter at AutoZone/etc.
Also, the headlight will yellow/cloud over the years, may be time for a nice new replacement.
Open the speedo and replace the bulb. It's pretty easy.
Again, clean the bulb casing & then use the goop.
HBI may need a new bulb as well, open the casing and check it. Again, it's not difficult.
It's good to replace ALL bulbs periodically. It's kind of like buying a used rifle...
First thing you do, clean it meticulously, then oil/grease where needed.
Second thing, replace all parts known to fail regularly...(especially bulbs & hoses).
Third, new Brakes, Chain/Sprockets & Tires. Adjust rear tire properly.
Fourth...ALWAYS have a spare starter motor on hand...this is NOT an item to skip when you have a Yamaha.
It will die, sooner or later, and you will need a replacement.
When it dies, slap the new one in, and at your lesiure, have the old one rebuilt at a local shop.
Fifth, always have a spare set of tune-up gear handy...and do one after getting the bike. Plugs, wires, points/condenser/etc.
Sixth...if at all possible, replace the points/condenser setup with Electronic Ignition...
saves you pulling out your hair But keep the old setup, in case of major sunflares/EMP attack.
Great thing is, once you do the total PM, it'll give you YEARS of easy riding with little maintenance headaches.
My Wifey's 1981 XS400 Special II