Using the crossover illustrated in you pictures, the only thing likely to need repair or replacement is the electrolytic filter capacitors (the little cans)
But you only do this if A) the cans have swell or ruptured, splurping electrolyte onto the circuit board or B) You have hooked the unit up to test equipment and determined that there is AC noise or signal crosstalk between channels that can be blamed on dried up filters caps. When they design gear the engineers know that electrolytics gradually dry up and over specify them a bit.
Replacing electrolytic caps is pretty easy. You should have a power solder sucker. You need to exercise caution to not damage circuit board traces.
I suspect that a large fraction of recapping done on the order of audiophiles is unnecessary. Audiophiles like to buy presents for their systems and on of the presents they buy, is rebuild and overhaul services. Kind of like buying flowers for your wife, or maybe paying for her to get plastic surgery.
The only way to check any of this is on the test bench. There are lots of non vintage active crossovers that would not need recapping. Vintage offers no adavantage. I notice eight op amps in the above pix. For a stereo unit that is not very many. Buy yourself a Behringer or a Drive Rack or a miniDSP.
Or buy three amps with built in DSP and you won't need a separate Crossover. (Crown's current slogan is "Installs Anywhere , Outperforms Everything!" Looks pretty close to true to me.)
The Fostex will NOT sound better. I know you are in love with it but I can show you a McClelland I have that looks just the same only more elaborate. It is essentially a Taiwanese no name. Same phenolic board, same op amps (OH NO! Chip op amps , lets' replace them all with discrete components oh my!!! Or do some OP AMP ROLLING
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Buying the Fostex would be a newb misteak. I sense it isn't what you want to hear. But you asked for advice. It will sound fine but the alternatives are better (the difference may be below audibility), more versatile and newer or brand new.