Better post pictures of the front suspension. It will need a front end long before 170k, perhaps a PO did it and you are unaware? It certainly helps resale quite a bit if it is indeed solid.
Not a DIY job for the faint of heart and I would venture to say a full front end at a shop with parts and labor is near $3000. Heck just buying parts from the various places online runs me nearly $600 per car I think now. A shop will charge you more, just part of the business.
Put a hood pad on it. This missing screams lack of care to me, from the owner. It will set you back about $75 with cleaning agent and quality 3M adhesive.
I am unsure if you can call MB and give them your VIN to see if the motor was replaced, it would be worth a call. This would boost value BIG TIME if you have a factory replacement in there.
Take about 30-50 high quality photographs in good lighting with the vehicle dry and run a vehicle history check, this will help you know your market. Just as-is, right this minute? I would not pay more than $2000. With more history, photos, documentation, that could (and should) easily go up.
Many years ago I tried to scoop up a black on black 350SD here as I love short wheel base diesel MBs. Bottom end was bad and I had access to a few, good 3.0 bottom ends to toss in... owner thought it was gold despite not running. I guess it ended up in the crusher.
