The dent MIGHT be fixable with a vacuum cleaner, or you'll ruin it. Only one way to find out.
Resistors may last forever, but you can always upgrade them.
Any electrolytic caps should be replaced. If you want to see about upgrading parts, check what was inside first. Then
read here to start.
As for the rest of the caps, if ever a speaker brand needed a Mundorf MKP it's these. They will warm up and smooth the treble. Of course, there are many Thiel fans here who will call this heresy, but that's how I hear them. After looking at the Stereophile charts and the constantly rising treble from 1kHz onwards though I'm not sure this would help enough. I'm not usually a big fan of Stereophile but in this case
JAs comments at the end of the measurements section is only a little charitable.
The point being, at best, MKP's would be the right direction vs. more revealing and brighter sounding caps. Personally I'd look for an opportunity to actually modify the crossover and point that treble down, not up. An alternative is the Clarity ESA's which may be even a bit darker.
Best,
Erik