Replacing Rotted subfloor and sole plate in bathroom

I am the process of fixing subfloor problems caused by a leaking shower in the second floor bathroom. One section that is rotted extends under the sole plate to the other side of the wall. I need to replace the subfloor from this side to about 2 inches on the other side, and this section of sole plate. To male things fun, that black pipe is a natural gas pipe and the shower water pipes are on the left. Oh Joy. The wall is not load bearing. I have been in the attic several times and visually seen the top plate. In fact I have sat on it and laid across it while installing a bathroom fan. Not sure how to proceed. to replace this small section of sole plate and the subfloor that extends underneath it. Because of additional rot, and the need to relocate the shower drain, I will be removing a section that extends behind the picture about 4 feet and two the left to the next joist where this sections seam is. I am just experienced enough to know I should ask for help on this one. Attachment 37210 (http://www.doityourself.com/forum/attachments/framing-sub-flooring/37210-replacing-rotted-subfloor-sole-plate-bathroom-photo-2.jpg)Attachment 37211 (http://www.doityourself.com/forum/attachments/framing-sub-flooring/37211-replacing-rotted-subfloor-sole-plate-bathroom-photo-1.jpg)