We got to see "Becoming Van Gogh" at the Denver Art Museum the other day...You must buy reserved tickets for a specific date and time. The best times to go right now will probably be afternoons because school groups have taken up lots of morning times during the week. The museum has been quiet on recent Sunday mornings too. The first 2 weeks are expected to be busy (the exhibit opens Sunday and runs for about 12 weeks)
There are audio guides available for a nominal fee (free for members). If you choose to use it and listen to all the audio, give yourself about 90 minutes to 2 hours to get through the exhibit and look at all the pieces.
Scroll down for our previous post on the exhibit. And here's more on the exhibit