I was thinking of maybe getting this 2nd hand fork to replace the one on a 2009 Cannondale CAAD9. Here's a pic below:

Mostly because it's got the full carbon steerer and should be lighter than the one I have now... ahhh vanity... I have no problem cutting down the steerer myself, but...

It looks like it has a fork crown race on there already (or is that just a collar that protects the fork crown?), and I am wondering if it is likely to work with the integrated headset that's already in the bike. I'm guessing this fork is from around 2003-2006? I am not experienced or confident enough to switch out the crown race from one fork to another, and it's kind of a bother to take it to the LBS. If I did go that route, approximately how much do you think they'd charge? Thanks!

That is a crown race, though it doesn't appear to be a bearing race for a loose ball headset. It looks more like the "crown race" of a cartridge bearing headset. I put crown race in quotes, because cartridge bearing headsets don't have a true crown race (that's part of the lower bearing" but rather a locating cone for the lower bearing race.

It will need to be removed. A bike shop will likely charge you just a few bucks to do it.

This race will require a specific type of remover since it doesn't overlap the fork crown at all and the usual hammer and punch won't work. You will need a "bearing splitter" type of remover and it's worth the few bucks to have the LBS do the job. Her's what the proper remover looks like and they aren't cheap: https://www.parktool.com/product/univ...e-puller-crp-1

Yep.......here's the tool that's needed sitting in one of my tool drawers near my work station. It's an almost comical tool, when you look at its size and weight, and then realize the little, specific job it's intended for:

You guyz rule! Thank you, that helps a lot!