Question: I've never played Pandemic, but thinking of getting the Legacy edition. Is it possible to play it without the legacy elements a few times first, and get an experience that is same or similar to that of the regular Pandemic?

Answer: 
Thats not true. You can play the game even after you finish the legacy version. Simply take out all the stickers that got put on during legacy play. They r really easy to take off.
Like people said before, it is easy to play vanilla pandemic with the pandemic legacy box. Moreover, various extra components/rules supplied with the game and gradually revealed through the game make it possible to play many interesting modifications of the game even after you finish the campaign.