Sprint Sprint T300 Project 1997

Hello all have recently bought a 1997 Triumph Sprint 900. It was a cheapie from eBay I bought as a project really. I have always fancied a T300 and this one popped up locally.
The bike has done 50,000 and shows it cosmetically. That sort of thing I can sort. The seller only had the bike for 5 months covering around 120 miles, said it was too big and heavy for him and I have no reason to doubt that. I don’t have any service records but I have tracked its MoT history and it’s only done around 1000 miles in the last five years. Brakes are relatively unworn discs and pads. Recent Hel braided lines, the calipers are clean as is the brake fluid.
It has a new Maxton rear shock.
Michelin Radial tyres that have about 800 miles on them from the MoT records.
Oil and coolant look reasonably fresh.
Fork seals done about 500 mikes ago but they are misting and may need doing again.
That’s as much as I know upon getting the bike. It starts easily and sounds like a T300 on tickover but sounds sweet when revved. I let it run up to temperature and the fan kicked in so is working.
I have no records of valve checks. So that is a priority, I have never done bucket and shim valves before but have done tappits on several occasions and am confident to do this bikes valves if I take my time.

So to my first question the neutral light and oil lights stay on very dimly when the bike is running and in gear. The neutral light does get brighter when the bike is in neutral and dims when in gear. I suspect a poor earth somewhere and or a faulty oil pressure switch. I can service and look after my bikes but could do with any help solving this problem. T300s are very new to me, I have Hondas.

Also where can I source a new oil pressure switch for the bike. I would post some photos when I work out how.
Regards Rob.