upgrading caps -- easy to do?

WAIT!!!
The replacement of the caps IN a speaker crossover is not the same as caps in a circuit in a electronic device.
The caps in a crossover have a direct influence on the voicing of the speaker, and swapping out the caps MAY alter the sound in ways you will NOT like!
Usually changing the inductor coils is less of a problen with alterations in the apeakers behavior.
I would be leery of doing the caps, And expect that you may need to experiment if you do!
Also see discussions about using small value additional caps to enhance ??? (don't remember, freq response or speed? anyway, plenty of talk on Audio Asylum in speakers areas, do some research there!)

You should get the crossover schematics if going ahead with the project. Some OEM caps don't tell what they are! nor do inductors!! A good source for caps and inductors is Micheal Piercy audio, also a couple of other places sell all the stuff... Inductors, caps, wire. The variety of caps you can use will make your head spin!! (AudioAsylum has sponsors, several of which sell these parts.)
If you can find someone who HAS done the same speakers with success, get those caps!
Good luck whatever you do.
(Rewiring is a GOOD idea. same places have wire available. I would use the wire in your favorite speaker cable, if it is available?)