The CD manual should provide a wiring diagram and component location guide, and probably not much more. On the other hand, that might be all you need. The manual should distinguish the 'with' from 'without' versions of the diagram. A caveat is that the CD manual is provided for US spec cars. If you don't have memory seats because your car wasn't originally delivered in the US, the manual might not provide the 'without' diagrams.

I would be concerned with the price and fitment of the parts you need (swtich panel, controller, seats). If you can't work the memory function into the seats you have, my guess is that it will cost you in time and parts the same as swapping your car for a car that has the features you want.

Good luck,
Sixto
91 300SE
... I konw my seats and my seats know me