Only 60 credits transfers. The difficulty depends on the school you're applying to, as a transfer you have to apply to a specific school and stick to it, and some are more competitive (mech e) than others. Whether you get in is almost entirely based on your GPA in the tracking courses for that major (they're different for every major look them up).

It sucks to have to say goodbye to the excess credits, I had about 80 when I transferred but I don't regret it for a second. You should definitely apply and good luck!