Oh and stop riding the existing wheel as you'll knacker the spokes by riding with them loose.
I'd say he's more likely to collapse the wheel than do any damage to the spokes.
If you are on a budget, you can undo the dent with an adjustable spanner, then loosen the loose spokes even more and hit that section of the rim with a hammer from the inside (protect it with wood ro something), making it more round again, tighten the spokes up to tension and hey presto!
IIRC a re-build at the Bicycleworks was £45+ depending on the rim a few years ago, I might not bother re-building on a crap hub though.