The Mac Pro is designed to be serviced very easily.
There is a lever on the back that you will flip up, which allows the whole side to be removed. Then, you can access the RAM slots right there, or move two more levers to slide the processor / RAM tray out a little, and move the RAM levers open to remove the old, and insert the new RAM in reverse order. Then, you'd secure the tray, replace the side panel and it's done.
It's very easy, I promise. However, if you REALLY don't want to have anything to do with the inside of the computer, you can take it to any computer shop, and someone there can do it for you, and you'll STILL pay much, much less for the whole process, even paying a computer shop to pop those RAM sticks in for you. Apple's RAM is *that much more* expensive.