I think it depends partly on what the rest of the system will be. The NAP90 is no powerhouse, and if you have a large room, play at high volumes, or have speakers that are not easy to drive, you would be better off selling it and getting something with more clout. Plenty of Chrome Bumper options out there - anything from a 110, 140, 160 up to a 250 would be good.
My main system is a 282/250DR, so this CB will be a sell on or a second system. In a smaller room, with suitable speakers (another debate to be had on them) it will be lightly used but a viable option.
Have you thought about this from the perspective of perhaps finding a power supply for the 62 and really making the combination sing? I don’t know the 62 but I had a 42/110 for a fair while and I wish I’d appreciated back then just how much better things get when a pre-amp has its own supply. I don’t think anyone outside Naim fully understood back then quite what a step up in performance it is; though God knows they tried to tell us! It takes things out of the “integrated” class into “serious” hi fi. Even a SNAPS will do it (if the 62 allows that) so you don’t have to be hugely out of pocket either.
I’m not sure why you are afraid to switch on the NAP90 but the first thing I would do is find out how the combo sounds now. Sure, it’s definitely had a long enough life to be in need of a recap but you might like the slightly more pipe ‘n’ slippers presentation of older caps. I used an even older NAP120 in a non-critical system for almost a decade and because it never put a foot wrong I look back on that system with immense fondness. I wasn’t setting any high bars for ultimate performance and it just delivered (unexpectedly, I should add) the perfect ownership experience. It got way beyond any question of value for money.
I wouldn’t put a £250 barrier in front of turning it on and seeing what it can do, and I wouldn’t sell it without doing so - especially as it’s now essentially for free.