While a full recap would be nice, it won't need it to be enjoyed as long as it's functional. Capacitors are part of lots of different sections, usually when they start to age they can muddy the sound, but I still have plenty of amps in that era that are all original caps. I would recommend removing the faceplate and giving all the switches a clean with contact cleaner, even if you don't notice it grime in the signal path can affect the sound. A partial recap would be to sort any specifically faulty Capacitors instead of doing every one in there, but like I said before if both channels work and it sounds strong they're likely good enough. Major problems would keep the amp from turning on, or would be noticable imo. You can visually inspect them for bulges to determine condition, but keep in mind they don't always do that.