I got parts from R&R Import Parts http://rrparts.com/
1-800-259-1271
Roy Tucker has been very helpfull and he has good prices.
The price was around $1200 - 1300
Yes it comes with the sliding cover. The complete part list is in the MB Work Instruction #280, available on Alldata.
I'm planning to install this weekend and can give more details on the installation next week.
Reg. Mike