From the sound of things, virtually any drive you might buy should eclipse the performance of the last drive you describe. IMO the debate is mostly about the finest points of DVD burner performance. They will perform well enough for you that the old PC will be more of a bottleneck than the new burner - so much so that I would be surprised if your system could tell much of any difference between any of the major brands of burners.
Don't fear the install. Just open the case, remove the old drive and take note of its jumper setting (3 positions possible). Jumper the new drive the same way as the old one was, then hook up the cables and power supply. 2 screws on each side typically hold the drive in. Might be some minor variation in cases especially with Dell/compaq/gateway - they like to make up their own mounting hardware. Once you've done this install, you'll look back and laugh, wondering why you didn't do it long ago.