Right, time for an update.
I haven't done anything regarding lights or tyres yet (I know, I know, I should have got on with it by now!) but I have just hit a problem.
After a few runs I thought it still looked a bit.....clean, so I made a big muddy puddle as part of the trail in the garden and the truck now looks much better! However, I fitted rubber sealed bearings when I built it to keep all the dirt out but the front wheel bearings have now rusted solid because of the puddle. Yes, I should have thought of that! They're soaking in WD40 at the moment to see if they'll loosen up but I'm not very hopeful.
So, what should I do now, assuming the bearings are dead? I've still got all the standard bushings that were never fitted so I might replace the bearings with those.
Any other suggestions, apart from buying new bearings?