Getting to the crossovers is something of a pain because the backs do not come off, you have to go in by removing the woofer.
You will want to wear something to protect you from the itchy rock wool lining, and if I were you I would take all the rock wool lining out before starting. Also put a dust mask on and perhaps something to protect your eyes. Once you have the lining out, get the inside vacumed out for any remaining fibres.
Once you have removed the woofer, by desoldering, you have to unbolt the crossover unit, this is the panel whose other side has the eq switches on it.
One issue here is that the nuts and bolts are locked using another nut, and it isn't at all easy to get everything spaced right when reassembling, be sure not to lose any nuts either.
You simply must purchase the correct size nut runner or the job verges on the impossible if you try it out with small spanners, or pliers.
I would get into it and remove just one nut, take it to a toolshop and get the right size of nut runner.
If I remember correctly not all the nuts you can see are there to hold the panel in place, some are there to hold the large dropper resistors in place.
This is a job in a small space and its very three handed, once you start you'll understand exaclty what I mean.
It will help if you have someone wih a screwdriver to hold the blots in place from the outside of the back panel while you unscrew them, and eventually when you tighten them.
I've only taken a look at the job, there was a resistor flapping around loose and it was a bad enough job putting that back in place.
I haven't had a go at doing the capacitors which will undoubtedly need doing one day. I would be tempted to put some solid state capacitors in place rather than electrolytics, you only want to do this job once - ever.