Hi mate I don't know a lot about the xr21 however:

It is possible to buy a new patch repair panel for the petrol cap for about £20 then cut and weld this in, fill and spray. A half decent bodyshop will want about £300 to do this. Or if your feeling really flush you can buy the whole quarter panel and have the whole side cut out etc. I know some one on here has done that in the restoration section. 1900cvh I think.

There are only 5 numbers on the speedo. If it's showing 34k but you are sure it's done more, and by your description it has it's probable 134k. ie it's been round the clock once.

Have a look in your owners manual or search the net to find out what your light is. This may point to your heavy steering or your running prob.

Hope this helps.