Actually I think this car is o.k. I would go for a slow restoration, why not. If you do the work yourself, and don't go crazy on new parts but, rather, source good used where possible, and shop around for paint work, it should be a fun and affordable experience.
The engine being a carburetted one does affect the value obviously. How much is hard to say; if it runs great, and you don't intend to sell the car in the next, say, 10 years, then the effect on the value to you is nil. On the other hand, if you do want to sell it, you will get the same argument that you probably confronted the previous owner with. The 250 block can probably be converted back to fuel injection.
Check the homepage, databases, parts and service supplier list. There are used parts sellers in there that could probably help you to a shifter. You can try our own Dr Benz (search in the forums for his posts, and you can send him an email).
I would seriously consider changing the color back to the original cream, which looks good to me from the photos.
Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic