Important halo 3 question

I’m planning to download halo 3 in July when it becomes free, just to eliminate my need for the disc(s). My question is this:

IF I do download the digital copy of the game, will it overwrite my current game data obtained from playing the disc? (i.e., forge maps, appearance, campaign progress, skulls found/available in menu, achievements unlocked, etc…)

I suspect the answer is “no” but I want to be sure before I do anything… (especially suspect the answer is “no” for achievements).

Nope! The data will carry over!