Proud owner of 1989 2.5 DT Defender Hardtop (new to Land Rover)

Recently bought a 1989 2.5 DT Defender hard top. Bought it for my wife as we live in a small village and our little boy goes to school in the next village. Wanted something classic and traditional. Always loved Land Rover but never had the chance to buy one. We love just jumping in it on an evening and just driving around the countryside for half hour or so. BUT its not without some issues...mainly electrical. Looking forward to any assistance we can get to solve the small issues.

We have a capput rear wiper motor. (round one not the flat newer one) Struggling to find a second hand one. New one is pretty expensive. Also the rear heated windscreen is not functioning connections broke off so not connected up. Fuel gauge is not reading correctly (3/4 is bang full) and finally Temp gauge not showing anything at all...worried part. Help needed please.