It's not really necessary; if you don't think you could stomach the kind of gameplay present in the first two games then don't force yourself to play them. I'm sure New Vegas will tell you everything you absolutely need to know; it's unlikely that Obsidian wrote New Vegas and ignored the fact that many players haven't played the first two games. When Marcus and\or Lily talk about the Master for example you'll probably get more out of the dialogue if you've played through the original Fallout, but I'm sure they'll give you a history lesson if you're interested.
The only things you really need to read up on in lieu of Fallout: New Vegas are NCR/ New California Republic, Enclave, Brotherhood of Steel. And possibly Caesers Legion, but as of now, most of it is based on Van Buren, which is not canon (VB is the cancelled Fallout 3)
Yeah, nothing from the Van Buren design docs should be taken into consideration for New Vegas;
especially elements from Van Buren that are being included. For example, there's no way the Caeser's Legion was formed by Caeser in 2238 because while that would have worked for Van Buren which was going to be set in the 2250s, New Vegas is set in 2281. The year the Legion was founded is probably more like 2250 or 2260 something now, maybe even 2270 something.