Sure. Get a basic computer from them, the CatEye Enduro is more than enough and is a solid choice. Shouldn't be > $35 (list price) hopefully a bit less. Anything from Planet Bike is good too. These are all solid choices and will last years. Don't go crazy on the computer; you may not need one at all (I have one and hardly ever pay any attention to it - what, are you worried you're going to exceed the speed limit?) but you certainly don't need more than current/average speed, odometer and time of day. Max speed is amusing to have and all comps have it. You don't need cadence unless you're training, which means you don't need it, and cadence runs both the price and complexity up.
Installing a basic computer is very easy. Just be sure to mount the magnet and sensor as close to the hub as you can get (no need to get silly about it though), and make sure that the wires can't touch the wheel or interfere with the brakes. Use zip ties or electrical tape to secure the wire, loop extra wire under the stem. If your bike has a suspension fork, make sure to leave a bit of a loop around the spring so that it can flex there and won't head into the tire when it does.
The trickiest part is setting the wheel size but if you follow the instructions that's easy too.
Nothing else outside of messing with the derailleur is even as hard as that. If you decide to start working on the bike yourself, wait for Nashbar or someone to put a basic tool kit on sale, you can buy it for < $40, and pick up the Park Big Blue Book of Bicycle Repair (or just use Park's website for help)
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