I'd build and clean up with the fork fitted while looking for another fork.
But if you stay threaded headset like you have then you shouldn't need new bearings (if it all feels fine, just a clean and grease) otherwise.
Headtube (length of tube on the frame the steerer fork goes through) will be 110cm and 1 1/8" headset fork
So for a new threaded fork you'll need 110cm + headset height.
So staying with that headset you just measure the current fork length (If I remember I can go measure mine).
If you get a new one, you just add it's height on to the 110cm.
If you switch to a threadless (ahead) setup it's a little more complicated.
It's headtube length + headset height + stem height, that's the minimum length you'll need. (as a guide 110cm + 30cm + 40cm, say 180cm then)
You'll also need to fit the new headset and find a new stem.