Sounds to me like a used tractor.
Metric bolts are available at most auto parts stores. Any bolt that doesn't need to be metric (has its own nut), I would simply convert to SAE if you don't have a ready source. Metric bolts are very easy to size, just stop into your local auto parts store and have them explain how the sizing works.
Your lights are probably fine, but would benefit from removing and cleaning. Most light problems are due to a bad ground, the ground usually being the bolt holding it to the tractor. Removing and wire brushing the attachment, then providing a clean surface before remounting will fix 95% of your light difficulties. If it still doesn't work, pick up a 12v tester (looks like a screw driver with a light and has a wire coming out the end) or a multimeter and check continuity. By grounding the clip (on the tractor) and touching the light socket center (with the light switch on and the bulb out), your tester should light up. If it doesn't, run a ground wire from the clip to your battery ground and try again. If it lights, you have a bad ground (see above), if not, your circuit is faulty. If the circuit isn't working, instead of testing the socket center, try following the wire back to it's orgin and test it there. (The reason the tester has a sharp point is so you can push it through the plastic covering and touch the wire beneath). Works? Replace the wire. Still doesn't work? Test each side of the switch. Only one side of the switch has power regardless of on / off? Replace switch. Keep following back until you find power and you will see what needs replacing. Just start at the light socket and move backwards.
Make sure you are not smelling a burning belt. If your alternator is burnt up, it's easy to replace. If not, it is easy to overhaul it by replacing the bearings and cleaning up the armature.
I think you have probably made a good buy and it sounds like you enjoy the process, which makes it all the better. My previous tractor was an Iseki TU205 4WD that I picked up cheap because it was broken in half. I removed the axles, engine and transmission, remanufactured the frame and it has survived exceedingly heavy use for years (loader). There isn't anything you can't fix on a tractor.
Currently working with a Yanmar YM240D. Really like it. Reminds me of a John Deere model M I used to use in the 70's.