I just started getting this rattling/ clicking sound whenever i turn on the fan, it seems to be coming from somewhere behind the glove compartment. is the fan easy to get to, or is a trip to the dealer required.

 

Probably some leaves or other debris that got in there.
You don't say what car you have, but if it's a GD WRX or RS you can remove the glovebox, and take off the white trap door that's behind there which is where the optional cabin filter goes. The fan intake is right behind/below that door so if anything is in there you should see it and be able to get it out.