www.airsoftshop.com is a good one i've worked with them before
also
www.combatdepot.com is a good site as well. It's based out of Ohio. I've met and played with the guy who runs combat depot. He's a good guy and his prices are reasonable.
As for a starter gun, go with an AEG to get a feel for the game. Gas blowbacks or GBBs are just as much as an MP5 and they don't allow you to get a feel for the game.
The best starter gun is an MP5. Almost everyone who plays airsoft started out with an MP5.
If you want a more pistol type AEG get a TMP or MP5k.
As for shipments being seized, that doesn't happen very often because of the care taken in shipping. Trademarks on the guns are covered and so are the boxes. Most places will guarantee shipments if they get siezed. Also, most places take the precautions so they dont' get siezed.