Your data is on the HD in the PC. If you can, burn any critical data before failure to discs. Otherwise, you can mount your HDs in ext. USB cases and access data from another PC. -OR- mount those HDs in another PC with proper connection. That can be a direct connection or use of an adapter to route thru the USB port.
To answer your ? directly, replacing the mtrbd. which the same type won't cause lost of data. I assume the DV6000 is a laptop and thus only the exact same mtrbd. will do, you have no wiggle room here. Either this method or what i explained above.
IMHO, youmaybe better off just leaving the DV6000 alone and go to another laptop. The DV6xxx series was a problematic one and offhand any fixes may work but return again or cause future issues.
If I replace the chip (motherboard?) will I lose all data on my hard drive?
Conversely, how difficult is it to retrieve the data on the hard drive? I'm only concerned about documents and vacation pictures.
I've already had the chip "fixed" (solder reseated?) 3 months ago, so I'm really prepared to replace the whole computer -- I just don't know how to get my docs off of it.