Going to be a long process
You're right there, I think.
You can spray paint the instrument cluster, but the glass look over each LED won't come back. This bike's lived exposed to the sun much of her life, it seems.
Wiring a mess is because of the undertail that has been fitted with the tail light conversion and not having the original underseat's tabs to secure each relay, wiring, etc. Remove the tail and tidy it up. If there's poorly done wiring, re-do it using the best crimp connections you can find. Also if there's excessive wiring, shorten it & solder any wires that need it or had already been poorly spliced together, coating each in heat wrap. - this will help return reliability in the wiring and may help you find what's at fault with it now.
Most wiring is color coded, so not too difficult to follow and see where there's a break, etc. Poor electrical connections & installation often seem to lead to problems on these bikes, possibly because there's also a lot of vibration being a big V Twin.
Good luck with your project.
Euro RC51 SP2: HRC WSB Ti Hi-Level, T1 Airbox & Snorkel, PCIII, Dymag CA5 Carbon Wheels, Ti64 Spindles (F, R & Swing Arm), Mori Link, Maxton GP7 Shock & Ohlins 832 Forks, Brembo GP Calipers & SBK narrow track (F), Braketech Disc (R), Brembo billet Underslung x 2 Brembo RCS, Tyga Triple, 7075 Stem, Probolt Titanium all over, Babyface rearsets, MR Complete Carbon Lineup, Custom Undertail & CBR 1000 LED, Watsen LED Indicators, Harris Brace, Giles clip-ons, Corbin seat, etc. 2013 BOTY.