Any one ever replace caps or modify there Xovers

There probably are dozens of us who have replaced x-over parts; I've done it to maybe a dozen speakers.

General advice is to replace lo-quality parts with hi-quality ones, but that advice is as useless as your question is general. Get to the x-overs, trace schematics, etc. Then we can help.

And we'd need a budget, too, as there's little sense to recommend you buy $300 of parts if you've have more like $100 in mind. BTW, $100 might be a good budget for the tweeter caps. My tweeter filters have about a grand worth of Teflon-film caps in them, but no one ever called me sensible. :-)

Yes, caps AND inductors. In my Infinity RSIIa.
It was a fun thing to do.
And you MUST have the schematic for the crossover or forget it.
It was very hard to aquire mine back when, and now it would be impossible, unless someone happened to save them. Infinity changed hands, and the dude who gave them to me is long retired.
You would have to ask B&W...?? or find someone who has the schematic for your crossover.

UH? Can't you just LOOK at it and draw the Sketch-o-matic?
The DCR for the inductor can be measured.....amp off and lift one leg.
The problem would be the inductor value. That, too, can be measured.

Start tracing wires.....and maybe take a few photos.