So how do I know if it is the belt or pulley? And is it easy to change?

Open unit and check them. If they do not spin freely and smoothly, replace them. It is faily easy

How do you open most stackable dryers to get at the belts,pulleys and drum

How do you open most stackable dryers to get at the belts,pulleys and drum

What you need to do is to remove the dryer and take it apart. When you pull it out from the wall and unplug it you will be able to see what you need to do in order to take it off. It is not that hard to do. Then remove top and front. Have dryer on its back to make it easier to get the drum out. The first thing you want to do is to clean out everything very well which means to remove parts that move air and wash them out with soap and water, including door and blower fan. Just vacuum out motor. Some dryers have a rear drum bearing and that can be causing your problem. You always grease bearings in a dryer with white lithium grease, available at any appliance or auto parts store. If the bearing is not scored then you can clean it well and re-grease it put it back in, but if scored, which it probably is, then get a new one as it is fairly cheap. You also want to get a belt for the dryer unless you want to do this again in a month or two. It is only about $5.00. Put it all back together and test the drum by rotating by hand to make sure you have it right because many errors can be made in putting it back together. If you have labeled all wires when you took it apart you will have no problems.

I forgot to mention that you can go on YouTube and see how to fix the dryer. For example look at:
http://www.youtube.com/watch?v=MMP7BW1lLs4 to see how to tear it down. Also:
http://www.youtube.com/watch?v=iBiRw-KElC4

http://www.youtube.com/watch?v=yFTZGgVisCI

http://www.electrical-forensics.com/Dryer/ElectricClothesDryers.html

http://fixitnow.com/wp/2010/10/09/whirlpool-dryer-model-le5800xsw3-wiring-diagram/