Windows 11 Upgrade

Limited knowledge of PC's but quite happy plugging things in etc. Got my PC Specialist build in 2017 and have done some storage drive upgrades since to a pair of 8TB drives (one live one back-up) which to be fair are filling up fast, I am a photographer so lots of storage drive space needed.

Anyway, The Win 11 upgrade has me concerned I need a whole new PC. Can anyone advise before I have to spend a fortune?

The Win 11 update checker says my CPU (Intel Core i7 7700K @ 4.20GHz) is not suitable for Win 11. Can I simply plug a suitable one into my motherboard (ASUSTeK COMPUTER INC. PRIME Z270-P) or would I need a whole new motherboard and then I guess I would need a whole new PC? If I can plug and play, what do I need?