I'd suggest you to keep the car instead of loosing big bucks...
Off the BMW web page the MSRP on a brand new 335 configured like yours is $44,800, with dealing on the sedns, I bet you can get it for <$43k.
The MSRP on the 328xi loaded like yours is $40,800, you can probably get it for ~39k.
Do you really think you can sell yours for 38-39k?
It is a beautiful car and a great color combo, but...don't throw your money...
By the way, how did you end up owing $43k on it -- how much was the price??? It is a 330xi, not 335?