Robin, first off, in looking at the existing pipe, it's location and look (although dark) makes me believe the wall is a 2x6 wall, as elbows do not fit in a 2x4 wall. From the picture i am unable to determine where the stud is.
Assuming it is deeper than a 2x4 wall, I am recommending a model 500 retrofit dryerbox or a 425 new construction box, installed as close to the center of the dryer as possible. Hurdle will be getting the existing pipe to move or jog over to the new location. You are welcome to call me with more info, but our Photo Gallery has been an excellent resource for others to visualize what or how others achieved a difficult install. See this link:
http://www.dryerbox.com/photo_gallery.htm Good luck, and so that others can learn from your condition, please take some more pictures during the install and add them here or email them to rick at dryerbox dot com Thanks