Business CD upgrade to NAV?

[haumana]

I have a chance to buy someoneʻs NAV widescreen that came out of a e38 2001 740il.

I have an early face life e53 2004 (mfg. 9/2003), that came with the standard sound system w/6-disc changer in the back. No NAV (obviously), No Bluetooth (since it was early production), and no DSP.

Does anyone know if it will be an easy swap out? The guy who is selling it is asking $300 (perfect working condition), and says he will works on BMWʻs and will do the installation for an additional $150-$200 (at his house) Is the swap out easy enough for a regular car audio guy to do (I have a cousin who can do stuff), or should I trust and pay the seller who "works" on BMWs?

Is it worth it, or am I just better off saving my money and doing something else to the sound system? Iʻm content with the quality of the sound, as I donʻt regularly try to blowout the bass or anything like that. The in-dash CD unit is already to be problematic with skipping and stuttering, and the display is starting to lose pixels.

If I do this swap, do I need to do anything else to get the Bluetooth/phone feature to work? The seller said that he thinks the e53 is pre-wired for it, but Iʻm wonhe swap out easy enough for a regular car audio guy to do (I have a cousin who can do stuff), or should I trust that the seller "works" on BMWs?

Anyway, I come to you gurus to help with any advice, suggestions, and/or caveats.

MAHALO!!