Will a dent on the bottom of a Venus to effect the boat's ability to track a straight line?

A dent will not affect tracking unless it cause a gross deformation of the hull which actually has a steering effect to push it one way or the other. This would be quite a big dent, or right on the bow or maybe stern. Tracking is more related to paddle skill than almost anything else, although some short boats, especially white water boats, are hard to track. Many kayakers paddle harder on one side or the other without realizing it. It can be hard for even an instructor to identify what is causing it.

Oilcanning is a fairly common problem usually caused by improper storage or transport of your kayak, especially if it's hot out. Gently heating your hull (either by laying your kayak upside down in the sun on a warm/hot day or by using a heat gun CAREFULLY) MIGHT pop the dent out. If you were dealing with a single-hulled kayak, a little gentle pressure on the area with the dent while it's warm/hot would definitely do the trick. Not sure how I would approach a double hulled kayak, but it would probably be a combination of heat and pressurizing the inside of the hull or heat and water on the inside of the hull...would have to experiment.