I wouldn't. Unless you are changing to a different transmission or a vert, it doesn't make any financial sense.
I say hang on to your car and maybe mod it a little to keep your interest. Otherwise you are just throwing money away for the depreciation hit you are taking. Furthermore, you have an E90--no more being made! Reason to cherish it more!
08 E90 M3 Interlagos Blue
99 E36 M3 Cosmos, #2--Sold
99 E36 M3 Cosmos, #1--Sold