Jerry Dollar teaches a wreck course, including basic penetration, through Bubbles Below. However, the two wrecks you mention are not appropriate dives at all for someone with limited experience. Lake Washington is very challenging, with a poorly defined colloidal silt bottom and some of the most miserable viz you will find anywhere. The Dawn sits at 120, and the PB4Y is by anyone's measure a technical dive, sitting at 150.
We do have any number of wrecks in salt water here that lie in recreational depths. We have the barges at Shilshole, the Possession Point ferry, the Anna Foss tugboat, a barge off Des Moines, and of course, all the small wrecks at Edmonds and the Honey Bear at Cove 2. Scott Boyd's Puget Sound Wreck Dives is an excellent book, and gives you an overview of what's around to dive.
I am not aware of any specific wreck diving group, but you might post on our local forum, nwdiveclub.com, and see if there are any divers there with a specific interest in wrecks. For the bigger dives, you really will need to get to know some folks and get some dives with them under your belt, so that everybody feels comfortable taking you to the dark, spooky places. There are no charters that regularly run to the Lake Washington wrecks, so it's a matter of connecting with folks with private boats.