getting ready to paint the lower case and I already have Imron and self etching primer,do think its neccesary to take it down to the metal before I prime? It has already been repainted but was not taken all the way down, most of the paint peeled off but the primer did not.

Yes, I would take all the bad spots down to bare metal. I use PPG dp40 primer on all the bare metal spots. Any fill primer, compatable with Imron will work after the dp40. Don't forget the Imron clear, makes the drives look nice