M600 oil leak + lights out

hi there- any help with the following would be appreciated:

i bought a year 2000 monster dark m600 about 6 weeks ago (ebay special). £1300 with recent service/MOT, new clutch, new electrics and battery- seemed ok. spent ages waiting for a 33bhp restricted kit to arrive from italy (£4.50 from ducati- much cheaper than the £170 fiinternational inlet manifold restrictors), eventually took it out for a spin.

it was runnning fine, all lights working, then i noticed turning right from t-junctions that the back wheel was slipping slightly. put this down to wet conditions and manhole covers. however it wasn't happening on turning left, then the oil light started coming on and off. given that the fuel light had been intermittently doing the same despite a full tank, i thought prob just ducati electrics. eventually put two and two together and had a look at the back wheel- oil all over the right hand side and the right hand side of the engine near the filler window. i was pretty near home so carefully made my way back then all the lights went out. no dash board, no front or rear lights or indicators at 9.30pm. brake light fine though. i worked out that i could have a tail light on if i gently pressed the rear brake, and that front light would work on dipped beam if i had the full beam switch in. got home in one piece. then, weirdly, the all lights worked fine when the bike was parked and not moving.

the guy who sold the bike changed the oil himself before he sold it but says he did it on a slope so probably didn't get an accurate reading from the filler window. hopefully the leak was just due to over filling. it seemed to be coming from where the oil pressure switch enters the casing.....at least is what a mechanic mate thought.

now the questions:

1) what are the probs with riding with too much oil? i heard problems with oil in airbox and engine seals. any other things i should be wary of? anyone have any tips on how i can check and sort any potential problems? i was riding for around 2 hours at 50mph max- mostly slower though- how long before oil overfill ****s stuff up? if i just clean the bike up, lower the oil level and ride it without a full check do i risk irreversible damage?

2) anyone have any ideas about where to source new oil pressure switches? i was told ducati ones are about £70...anything cheaper out there?

3) is it possible the lights going out could have been caused by actively leaking oil? (this would explain them working when it was parked). leaking oil drenching electrics? will i have to get the electrics looked at as well?

cheers, and much appreciated if anyone got any ideas.