Army to Marines questions and potential problems?

You can wear any authorized ribbons in any uniform of any service MINUS the combat badge and if you have it, it does NOT transfer into a Combat Action Ribbon (the Navy/Marine equivalent of combat badge). Nor does a Sailor/Marine C.A.R. ribbon transfer to a badge in the Army, they both must be earned while in that branch. A medical discharge would put you into a far lower priority for enlisting. Contact a recruiter for sure.