Agree with above. You need to make sure the light and electrics are waterproof, but complete replacement at a dealer will cost far more than a local mechanic. Ring around local garages, explain and ask for costs - they may be able to do it very cheaply (espedcially those traditionally thrifty Scots, LOL). OTOH, if you need an entire sealed unit, that will cost you, alas - been there, done that!!

Good luck.