I am a tech in the Trauma/Burn ICU (I know...not very creative on the UserID) while going to nursing school
. We do have agency nurses in our unit, quite a few actually, but I have not run across any per diem in our unit. That might be a possibility through the CSR division. Your best bet would be to call a recruiter.
As to how I like it-I love it. I don't know much about the other ICU's, but SICU is somewhat of our "sister" unit, and I have heard good things about that unit as well-since you are a SICU experienced RN. My personal experiences have all been good for the most part, and I do recommend it to fellow nursing students as a place of employment after school quite regularly. There are units that might not be quite as good, but that is the case in every place of work, and I don't know of any in the ICU's.
As for parking, yes there are some parking lots that require taking a bus. There are options available that allow you to park in the structures near the hospital on the midnight shift only. It costs some $$ but is well worth the time savings. It seems as though parking is a hot topic with UofM, but you have to take the good with the bad.
Let me know of any other issues I can help you with/didn't bring up in this post.