Hi,
Using the mouser BOM and the boards from OSHPark is very easy to do, as every part in mouser shipping package is identified and refers to a unique place on PCB. Nevertheless, you need some advanced soldering skills as most parts are SMD and RN52 isn't the easiest part to solder.
Once the module mounting is done, you need to upload Karlis codes (RN52 programming) to adjust RN52's settings, then replaces the code with the SAAB-CDC and play music in your car !
To upload codes you need (at least) a FTDI-USB cable and the Arduino-IDE software.
Karlis codes are available in the software part of this great forum.
Or you find s-o able and keen in building one for you
Good luck
01' 9.3 SE Conv - AS3 - Nexus 5 Android M 6.0.1 - BlueSaab v4.2 + Amp - Latest CDC repo.