For a slightly warped wheel, is it worth getting it repaired?
Trueing a wheel is something you can do on your own, but until you get good at it it'll take you time to do it right - "carefully tighten the spokes on the opposite side..." is kind of an oversimplification. Typically a trueing stand is used; the wheel is placed in the stand and prongs or arms on the stand determine exactly where the wheel is out of true.

The problem is that sometimes you need to loosen some spokes to get enough play to pull back against the deformation enough to straighten it out. Someone who does it all day makes it look easy - you bring your wheel in to a good bike shop and usually it takes longer for you to describe the pothole you whacked into than to actually true the wheel. If you've got a good relationship with them they may not even charge you for a 10 second job (karma would demand an offering of beer or pizza as appropriate).

If you don't have a trueing stand but you're feeling adventurous you could try doing it with the wheel in the frame - stand behind / in front of the wheel (so you're looking at the tread) and spin the wheel slowly - you should see where it comes out of true. Use an actual spoke wrench - if you use pliers you can round the ends of the spoke over and if you use a wrench you'll put too much torque on it (I have a friend who has done it with a leatherman in the middle of a ride but he also repaired and managed a bicycle store for many years). 

Since it's an inexpensive wheel if you're confident enough in your abilities I'd say go for it - worst case is you end up replacing the rim, but you may learn a new skill in t he process.