Well as far as pictures are concerned, a few of our members have pictures of some of the engines, Amfleet, Battalion51, and Viewliner come to mind and each has links in their signatures to their sites. There may even be additional members who have shots of the locos, who can post their links.
As for spec sheets, GE provides a limited amount of info on their site. You can link to that site by clicking here. Note that the series I listed on their site is the P42 engine. The series II is the P32 AC-DM engine used for Empire Corrridor service only, while the AMD103 is the P40 engine.