I own a 1995 GMC Jimmy. I've noticed a lot of squeaks coming from the rear suspension as well as the door panels. I have called GM who informed me this is normal for this type of truck. I have brought it back to the dealer a number of times, but the noise still persists.
1995 model year GMC Jimmy and Chevy Blazer did have problems with front door squeaks. A hard plastic part of the door's weather strip was rubbing up against the body between the forward part of the door and the "A-Pillar", where the strip meets the chassis.
The best way to eliminate this noise is to apply a stick-on rubbing strip to the body at the point of contact. This noise is certainly not normal. Perhaps the GM representative you had spoken to was referring to the squeaking you get out of a lot of American made vehicles due to the low quality plastics used in the manufacturing of interior panels. The best way to deal with these noises is with a large can of silicone spray lubricant.
Now we come to the sounds from the rear suspension area. A common squeaker back there would be the parking brake cable rubbing up against the chassis under the truck. This will require the repositioning of the cables. Heavy duty wire ties (tie straps) work really well.
These are the most common causes of the noises you've described, but of course, there are always other possibilities that can take even the most qualified technician some time to track down.