Hi, Paul and welcome!
1) It's dead easy to change the interior light. Gently prise off the lens (between the sun visors) and remove the bulb ('festoon' type - available everywhere)
2) Could be power steering on the way out... Check the fliud reservoir and top up if necessary. Operate the the steeering lock-to-lock a couple of times and recheck the fluid level.
3) Could be a blown fuse. Fuse box is under the bonnet up close the to windscreen on the LHS
4) Unless your GF's a speed freak (in which case why buy a cabriolet...?

), probably not..., but it's your/her money...
5) It's much easier and cheaper to change the bulbs for 'high brightness' ones.
6) The dash lighting is pretty pathetic. You can use 5 W wedge bulbs in place of the 3 W originals, but they do get
very hot and can melt the fitting. LED bulbs don't seem to be much better, but you could try the 'stacked' 5×SEM (at least)... Also the silvering on the light guides in the dash module can crack, flake off, discolour, in which case no bulbs will help...