I’m looking to change the forks on my fiancée’s MTB for something a little more plush and have a couple of potentially stupid questions… If buying a used pair of forks with the same size steerer:
1) Do I need to change the crown race? Is this headset specific?
2) Do I need to change the star nut? Again is this headset specific?

I’m reasonably competent at DIY but given I don’t have the correct tools for removing and installing a star nut or the race (I’m sure I could get by with some improvisation) is it better to take it to the LBS? If so any ideas on how much time it would take a pro to get the job done?

1) yes & yes
2) No & No.

I don’t have the correct tools for removing and installing a star nut or the race

You don’t have a flat bladed screw driver and a mallet(hammer) in your tool kit?
(maybe a stanley blade to start it off, if it really tight and no notch on the crown to help)
I’d suggest this is a job any home mechanic can complete [aka it’s a piece of proverbial ****]

stanley blade under the crown race is good.

use a bit of plastic pipe to fit (or the vacuum cleaner tube if it’s for the GF’s bike).

1-yes See here
2-no, what he ^^^ said

Two of the easiest jobs on a bike- do it.

I hate removing crown races. Last time I just took it to the LBS and they did it for free as I was buying new road brakes.

Well when I said proper tools a google search suggest a crown race puller… and by improvising I meant my trusty hammer, screw driver and vice 😆