I'll answer the pelican one.
If you want to fly it in Multiplayer then I don't know.
Single player what you do is drive or fly a vehicle on silent cartographer or other levels with them in, then when you get to a checkpoint inside the vehicle exit the game go to the hex workshop then input the ie; warthog (or whatever vehicle you are in to the pelican value over the warthog value. Then you should load your game back up and then you should be flying a pelican.
I havent done this but as far as I know this works, but I think one problem with it is that if you exit the pelican you can only get in the sideseat (back seats) when you wanna get back in so you will have to do it all over again.
I hope that helps you. For any other additional information regarding modding or other halo modding (just modding) then I will be glad to help by sending me a email to
Onimusha__Blade@hotmail.com or adding me to your MSN contact list, either way I would be abliged to help you in anyway up to my vast knowledge of modding.