Noise in plastic cover on the motor.

Need to know which engine you have when discussing engine-related stuff. The 2.5L 4-cylinder and the 3.0L V-6 both use timing belts and noise from them is not common.

Also need to know if your serpentine belt uses a spring-loaded tensioner pulley. If you don't know what to look for, grab the belt and tug on it. If you see one of the pulleys move, and it moves back, (hopefully), when you release the belt, it has a spring-loaded pulley. The 2.5L has the alternator mounted on top, in front of the engine, on rubber bushings. There's a fix for those if they cause a squeal. If you have the 3.0L, you also have to check for a loose air conditioning compressor belt. That one must be manually adjusted.

Are you sure that's not a 2.5L? They look the same on top but the oil pans are different. Regardless, there's two nuts to take off, then you can slide the plastic top half of the cover off the timing belt. Check the sides of that belt for fraying, and feel it for looseness. It would be very uncommon for it to come loose.

For the alternator belt squeal, use a pry bar to move it sideways a little while the engine is running. If you move it one way and the noise gets worse, and the other way the noise goes away, remove that long bolt to install a washer under the bolt head, or just remove the nut to put the washer on that side, then tighten the bolt again. That washer will force the alternator to move sideways a little in the rubber mounting bushings. It only takes 1/16" of misalignment to make a serpentine belt squeal.

For most of these that I did, the washer had to go on the bolt head side. To cheat and make the job go faster, I had a few washers precut with a slot so I just had to loosen the bolt to slide the washer on. Didn't have to pull that long bolt all the way out.