My old PC is really old but it was built with high quality parts so it would last......................Looking to put this 13 generation CPU into a case containing a Gigabyte Z790 UD AC motherboard.
Don't know how old "really old" is; can you name the current CPU?
In all likelihood, a current generation i3 would be fine.
BUT, you have to consider that you will be exchanging apparently still OK "high quality" parts for new parts of uncertain longevity. You may have issues with the new parts within weeks or months that you would not have with existing parts.
That is always a possibility of course with new parts. You just have to make a leap of faith.
I'm in the same boat myself...7 year old CPU and motherboard still performing perfectly and more than adequate for my needs. I continue to say "leave well enough alone and don't replace them". But I fight the impulse daily.
Edit: I just checked benchmarks comparing a current generation i3-13100 against my 7 year old i5-6600K.
Single thread: 60 percent advantage to the i3-13100.
All threads: 138 percent advantage to the i3-13100; more than double.
I do the same stuff with my PC as you do. No gaming. My 6600K is more than adequate for what I do. I wouldn't think you would need a current generation i5, but budget may allow for it.
Do you already have your OS on an SSD?