Dryer squeaks, does not dry properly--takes 2-3 times longer than usual

All driers will do that when the lint builds up like concrete on the inside of the air ducts. You need to totally tear it down and scrape out and wash all of the parts except the motor, which you vacuum out. Halfway doing it will not work. This includes the exhaust vent, all the way, even the outlet on the side of the house, if you have one. If a safety blows, you will also have to find the blown safety with an ohm meter. You cannot guess and just change parts. You can go to YouTube to see videos on how to take it apart, but do a very good job or it will fail again quickly. I would get a new belt and change it while you have it apart and get some white lithium grease and grease any bearings you find. Obviously, you need to grease the bearings, if they are not already scored and ruined. I think your dryer has a center drum bearing and support rollers which all need greasing. You need to pull the support rollers apart to grease the pins with white lithium grease. The center bearing may be ruined if it has dried out and therefore order a new one, but do not use it because it will blow a safety which is expensive to replace. You need to clean out a drier every year, at least, according to the manual. All sensors work together by comparing temperature, so all need to be cleaned. You just unplug the wires from the sensors and remove ductwork that they are attached on and clean the entire thing with soap and water. Make sure you go all through the dryer and get all parts like the blower fan and housing, vacuum out motor well and clean exhaust. Mark all wires you unplug so you know where they go. This is an easier job than you would think. You need a meter to test any fuses that may be blown. You will see them on the schematic diagram.
See: Dryer vent cleaning prevents fires - YouTube (http://www.youtube.com/watch?v=A6wmD502-xE) and: Cleaning out a dryer with top lint cleanout - YouTube (http://www.youtube.com/watch?v=OBNDbyRm68M&feature=fvsr)
Cleaning out a dryer: By a woman 2 of 2 - YouTube (http://www.youtube.com/watch?v=a73HTFkcB90&feature=relmfu)
Manuals:
https://dl.dropboxusercontent.com/u/8010163/Frigidaire%20Dryers%20Gas%20and%20Electric%20Elect ronic%20Controls%20.pdf
https://dl.dropboxusercontent.com/u/8010163/Frigidaire%20Dryers%20and%20Test%20Equipment.zip