Make sure U have ur valid I-20 with the advisor's signature of ur new college with u. Until then U will be fine, because some of my friends have also done that and they had no problem at all. The best person to discuss about all these is ur new international  student advisor. Consulting few lawyers who offer free consultation is not a bad idea, but is unnecessary I guess.
      when u get ur I-20, I dont think employment letter or bla bla bla. is necessary, because the issue of a new I-20 automatically disables ur OPT.

 There is no big complication in ur situation, so take it easy and I wish U a safe and enjoyful trip to Motherland.