Advice? Don't double dip. If it is going to be published, the 'correct' thing to do is to retract it from either the journal or the conference. In reality, most likely nobody would notice, but they potentially could. You have to read the exact rules for the conference itself. Virtually all of ours have the rule that if something accepted to one of our meetings, you are required to submit the manuscript to that society's journal before submitting it elsewhere to prevent people from using the conference for exposure to work that will be published elsewhere. It just depends on the exact rules.
If it is against the conference rules, you and any other co-authors can be blacklisted and prevented from presenting in the future. Typically for a certain amount of time. Not that big a deal for a medical student, a bigger deal for more senior authors. It does look like a pretty bone headed move and I could see it potentially hurting a residency application in the same specialty if someone were to remember. But, that risk is pretty damn small.