Congrats on making it to your last semester! I'm going into mine, too. We had critical care this past semester. No, you won't be ACLS certified. You'll be reading strips, and getting to know a bit about vents and different meds than in med/surg.
Don't stress too much. I have zero desire to go into ICU, but I did okay. I didn't realize my instructor would want 42,000 sets of vitals on my write up, or the vent settings for every ABG. You're paying attention to different stuff than you are in med/surg.
How long are you in ICU for clinicals? For us, we all rotated through for a week apiece, so it wasn't too long. Just be open to new experiences (like any unit!), don't touch any machines without the RN's explicit okay (the RN I worked with the first day was fine with me changing out the bags on the CRRT and showed me how to do it, the RN the second flipped her lid when I went to do it and complained to my instructor).
DON'T get overwhelmed! You really will be okay! You'll have a lot to draw from being in your last semester, so you can just focus on what's new. A lot of the classroom stuff, like learning about the meds and vents and such actually will come in very handy in ICU, and the nurses will help you learn everything else. Breathe!