whenever I start up the vehicle sometimes there's this squeak type noise coming from under the dash that sounds like it's speeding up and then the fan works normally, and it goes away if I switch the fan speed up to high

I'm fairly certain it's the fan . . . what sort of job am I looking at to replace the thing?
I had to replace the fan on my Corolla a couple years ago and had to really dig into the dash to get that one out