Pft, 30 minutes is easy! You can do it. Try two hours with 2 out of four groupmates ditching you the morning of the presentation. That was a true cram, aced it (sympathy helped I'm sure but we did a damn fine job all things considered).
When I really have to get ready for something like this in a hurry, note cards save my life. I divide up the presentation into 5-minutes per notecard and write down about five points on each note card covering one aspect of the topic. Bring a couple of extra note cards and leave yourself time to practice it....preferably at least twice but in your case it's looking like once. Good luck!
And yeah of course Q&A/small groups helps but for 30-minutes...nah, you don't really need it. It will be obvious you are unprepared if you switch to Q&A halfway through or something (although I'm not sure that suggestion was entirely serious), but if the prof isn't providing room for them afterwards, 5 minutes looks classy, not unprepared.