I have a Kenmore stackable dryer, model number 417.8004299 that is making a squealing noise, is it a bearing and can I repair it?

It is most frequently not a bearing but rather a glide on the drum allowing it to rub as it turns. Here is a parts listing for your dryer. Looks like the 2nd part is the felt glide. http://www.searspartsdirect.com/partsdirect/part-model/Kenmore-Parts/Dryer-Parts/Model-41780042991/0582/0151200?searchedModel= 417.8004299&blt=

In both side of the drum you have rubber wheels look like rollerblade wheels it's possible that the rubber is worried down and the metal is hitting the case
Open the front and remove the drum

http://www.philadelphiasubzero.com

Once you take it apart you should be able to see what the problem is and fix it. That dryer shows a drum bearing that is lubricated with white lithium grease, as are most parts on the dryer. There is also an idler pulley/ belt tensioner that may need lubrication, too. If you will tear down the dryer and clean it well you will be able to see what is bad, and lubricate the other moving parts with lithium grease. You really need to be very thorough and clean every place air flows to remove caked on lint deposits such as near elements and the blower fan and housing. If the rear bearing is bad it is easy to fix. I would change the felt liner as well because they wear out. Once you grease everything and put it back together you will have a quiet dryer that will even dry faster. Check the vent when you clean it and make sure you clean it out well.