Hello mbzkid
The 300SD parts are the same price, and there is a little more to go wrong.

Do you think I could get this car for less than $3,500? http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=6330&item=2496070508&rd=1
Yes, you might get the car for $2500.
Call and offer $1500, have your parents coach you on dealing, it looks to be worth 2.5k...

This is a nice looking car also.
Heres the 300D- http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=6330&item=2496301994&rd=1

A W116 came before the W123.
Even if the turbo dies, check closed sales on ebay for used turbo, the price is lower than you think.
Turbo R&R is a Do It Yourself (DIY) job, ask 1985 300SD SADY, he is 15 and his name tells what he has, read his thread.
wont start for anything! 1985 300SD

The 1985 300SD W126 is what I drive and like, a W110 or W115 would be welcome in my stable also.