If i go into the Delayed Entry Program for the USMC, can i be guaranteed a MOS?

The last answer was absolutely correct. If your active duty then 03xx is what you will go in as. However you don't need to worry about getting 0311 you just don't volunteer for a weapons MOS at SOI. You will have no problem staying an 0311 since most people are trying to get into the weapons MOS's.