cny-bikeman raises a good point. You'll notice that I said it depends on the nature of the bend. There's a subtle distinction between a bent and a warped rim, the issue being how local bends are and and how much local force is needed to overcome them. Warped rims (looks like a potato chip) come back pretty nicely, but a local bend like from a pothole needs big differences in spoke tension to compensate for the rims desire to stay bent.

If you're willing to undertake this as a DIY learning experience, you can probably get it decent if you're patient and bring it home by degrees. Don't crank down on any few nipples trying to bring an area back to center, but instead work broad areas bringing the worst up to the 2nd worst, then continuing by always just bringing the worst areas in a bit, as you work around the rim. Be sure to work from both sides toward the middle. When you get reasonable close, you'll want to confirm that it's dished to the center of the hub (not the flanges of a rear wheel).

Good luck and don't get flustered.