Is there any pic of single din retractable HU mount on metra kit here? should I go w/ DD or SD, thanks for any opinion.

I don't know of any pics with that. When you've got the option for a DD, I don't see any reason to go with a SD headunit. Many of the SD retractable units use a hideaway box for some of the electronics and that's a lot more hassle. The DD unit will be a bit tighter fit in the space behind the kit, but it looks nicer once installed and won't be nearly as difficult as a SU with hideaway.