My fan will stop or stay at low rpms despite high temps.

I have a late 2008 a1278 unibody 13inch macbook. this past 2 weeks I started noticing that the fan was making alot of noice, using the ifixit guide I opened it up to clean the fan, which resolved the problem, yesterday I noticed the fan was really loud and the body was really hot. I installed a widget to track the temp and fan speed and noticed that despite the computer reaching 80 degrees celcius the fan was extremely noisy but only reaching 2000 rpms, then it reach a point where the fan started sputtering and was doing about 150-300 rpms. Would you guys think by simply replacing the fan, I will solve my issue or should I worry that there are far more serious issues going on?