This was my first time to the Hoover Dam, it is fairly close to the Strip. The drive is pretty fast without traffic, you should have no traffic heading out of Las Vegas either way. There are many tours you can attend when there, however, I was on a time constraint so I did the solo self tour/run around.
There is free parking if you follow the route all the way to the end of the Dam. The area is usually packed with people, but its not too bad and people are willing to help you take pictures when on your route.
But people really come here for the view, and its is nothing short of amazing. There is a sky bridge that oversees the whole dam which is quite a sight. There are also observatories for tourist to take pictures in front of. If you're in the area and want to kill some time before heading to Vegas, or want to take a tiny break from Vegas than come check out the Hoover Dam.