i just finished reading the feed on warranties and it concerns me a little, however, i have a mechanic here in sudbury who is great... ( he worked at a bmw dealership...) and i agree the option of banking the money otherwise spent on the warranty and go from there....
I am sure your Bimmer mechanic in Sudsbury is first rate, but a 2004 330 with a SMG is a far cry from a 1998 328. Your guy will not even be able to read the codes. I figure there is probably only one senior tech in any given BMW dealership that can work on that tranny because of the newness and complexity of the thing.
Without question you should get the VIN and phone the BMW dealership where this 04 330 was bought and serviced and confirm that all necessary service work was done to it, particularly the tranny.
Since you say Sher way Accra is at least 5 K cheaper for a better car than any Bimmer retailer, then just to be squeaky safe, run your own accident check.