You can test the headlight independently by connecting the tabs direct to a 12v battery to see if it's the light or something on supply side of bike.
Usually three tabs, one earth, the other two for dip/main filament. As long as connect just two at a time you'll be able to see it works.
Don't accidentally touch the two wires together though

Brake caliper. Undo the two bolts that hold the caliper halves together, undo also the fine adjustment screw, then you should be able to assess if the arm is stuck, ie not swinging. If that bit is ok, then it will usually be the piston/pad/seal corroded or stuck. It's not that complicated but would involve a strip and clean followed by a bleed through to bring it back into use. No real shortcuts there for this.
Have a look and post what you've got for further advice.
