I don't know you or your mechanical aptitude, but I can say that if you can ride a motorcycle, you can change it's oil. Especially on the Rebel being a naked bike, mostly everything is exposed. It's far easier to change oil on this bike than any car.
If this is your first time getting your hands dirty then it's time to learn. The tools you'll need and will use for many years to come costs a fraction of the $120 you're quoted for. It may seem daunting at first but once you're done you'll be thinking, "I almosted paid $120 for that?" The cost on investment of the tools is instantaneous!
In addition cleaning the chain is something you have to do really frequently, depending on much you ride actually. The rule of thumb is clean the chain every 600 miles, and lube every 300. Forget about the cost for a sec, your bike will be sitting in the shop anywhere from a half hour to several hours, not to mention you actually have to go to the shop for something you can do in the comfort of your own home in about 10 minutes.
Also it's fun to work on your own bike. I enjoy it and see it as my source of 'zen', most importantly I know exactly the products I use and what goes into the bike. Just my 2cents.