One of my fans on my Radeon HD 6950 isn't working

As per the thread title, one of the fans on my Sapphire Radeon HD 6950 has stopped working and on top of that the one that still works (which is over the GPU) is not really speeding up when it has to and makes some weird clicking noises sometimes.

I noticed this about a day ago after playing wow and having graphics lag after playing for 30-40 minutes. I initially thought I had a memory leak issue going on somewhere but I installed some temp monitors to check CPU core temps and my GPU and noticed the GPU was at 90C and I bugged out.

I'm thinking I can buy a can of duster and spray into the thing to see if dust messed it up but does anyone have any other ideas? If I need to get a new cooler how hard are they to install? I've never replaced GPU fans so it worries me just a bit. I also have very little clearance between the GPU and the bottom of my case as I have a mini (or micro?) atx case as well as a super tiny mother board.

Any feedback would be appreciated. Thanks