Macbook Pro Fan Problem

I own a 2009 13 inch Macbook Pro and for the last few weeks its been making these weird noises. It got to the point where it was so loud it sounded like it had a motor running. I've had it for almost 4 years and never had a problem with it. I will add a video to this post. I have now since then opened it up and blown air through it and got some serious dust out of it. It kind of stopped but when I open my Macbook Pro it does it again. Only for like the first few minutes. Anyone know what else I can do to fix it? Like I said I will add a video to this post so you guys can hear how loud it was.


http://s13.photobucket.com/user/rat5/media/2F680A39-B8E3-4054-BEDE-B654E01A60DE-2233-000000B303BF388D_zps346d1f50.mp4.html

 

it only happens for the first few minutes when i open my computer... and it starts to fade away slowly...

 

awww dangit! lol are they expensive? hard to replace? i only see one big fan...

 

i can probably do it myself... just hope the fan is not expensive...