Just completed a dealer retrofit of a TCU bluetooth retrofit into my 2006 - 323i (e90).
The total cost was $1800 which included $1100 of parts including the TCU, FZD and all brackets/mounts. 4 Hours of labour was charged for the install per BMW recommendation (however this was the 1st retrofit install for the dealer - they spent about 8 hrs in total due to unfamiliarity with the programming process).
The system works great! The bluetooth paried seamlessly with by blackberry curve and BMW Assist / SOS is operational.
After many hours of sourcing info on this forum, my recommendation is to have an authorized dealer supply all parts and do the install. My SA said the programming was tricky and several attempts had to be made for all components to be recognized. They had to contact BMW head office to troubleshoot some install issues.
Well worth the investment,... Good luck all!