Just had the engine replaced, now my O/D off light is blinking and it's shifting hard and feels like it is slipping some. I have unhooked the battery to try to reset it , but it didn't work.

 

Most likely your tranny is going out. When mine went out (2 months after i bought it... :( ) mine was flashing like that. It means there are codes from your tranny. When I finally had mine checked, it showed every gear had an incorrect ratio(meaning missing teeth).

Check the codes, and hope that its an easy fix.