In answer to your question, everyone on here has a valid method for removing the glue from the doors... just use common sense when picking out a chemical to remove it with... don't go for something like "stripz all" or something that will take anything and everything off... elbow grease may seem like a pain, but this is a one time deal... and saving the paint will pay off in the end.
I do not know if I agree with pulling the guards off.... but if you do, please be careful... I know a couple instances where folks have removed glued on trim items by pulling, and have resultantly pulled off some paint too....
As I said, just use some common sense and all should go well. And I do agree, the car does look 100% better without them!

-Jeremy