Welcome!
Brakes: leaks at the caliper are either the inlet hard line is somewhat stripped at the threads (if the leak is appearing where the hose enters the caliper body) or as Faux said, the piston seal. Be mindful when disassembling the caliper of two things: 1- brake fluid eats paint immediately. 2- the bolts used to assemble the caliper are a very fine thread and you can muck them up pretty quickly if they're not aligned. Use some AntiSieze when reinstalling them (just a tiny bit) to help lubricate the threads for better protection from galling or stripping.
Fuel issues: RedKote can tint fuel. You will have to drain your tank to remove the petcock. Don't know the rebuild kit, but should be fine. SeaFoam is fine, probably can lay off a little after the rebuild if the bike is running well. I use it every 3rd or 4th tank, but not constantly. Up to you.
Engine clicking: couple of things to check- cam chain adjustment, drive chain slack on the sprocket, valve adjustment. All of these maintenance duties should be performed ASAP to protect your investment. Always consider them having been overlooked and not done recently.
Speedo/Tach - both of the gauges are mechanical and are driven off a cable. The speedo runs to the front wheel, and the tach should run to the engine, front side, into the top cover. You should find a mounting boss between cylinder 3/4 up high on the face edge of the valve cover. Maybe it's been removed by the PO?
Final drive - a picture of this would help
Aluminum oxidation - welcome to a 35 year old bike
It's a major effort to remove and restore the aluminum with the engine assembled. First, clean it well with a degreaser. Then, start with some dry paper, and clean/sand until the black pitting is gone (this will take some time). Once the pitting is gone, progress up with more fine paper (I use the rule of doubling the grit, first step 200, 2nd step 400, and so on). Each successive grit removes the scratches from the prior grit. Depending upon how shiny you want, you can probably stop around 1500 and just polish with Mothers.
Fins - if they were painted black, then Back to Black won't work. B2B is for plastic trim, not painted surfaces. Just clean, scuff, prime and re paint with a rattle can as best you can.
Water and motorcycles - not the best idea, but they can get wet. Be frugal with blasting it and protect your spark plugs, coils, and ignition. Dry afterwards and start the bike and run it immediately to dehydrate any moisture from sensitive areas. You'll be fine.
Hope this help!
