Can I rotate part of the mesh while reserving topology? So, I have a mesh (a tie fighter, actually) with this plate on the end:


Sadly, the plate is misaligned with the rest of the spaceship.  I need to rotate it.  However, this drags the vertices that lead from the arm to the plate and leads to some very funny results.

I suppose I could detach it, rotate it, and then reattach it, but then it would no longer truly be connected to the rest of the mesh.. .and I'm ramping up to model for a 3D printer, so I'd like to work this out!
Its actually simple :)

First select the edge loop you need to seperate with Alt+RMB as shown in the picture below.



Then select the other remaining edges by right clicking on them....

When you're done selecting just the plate press P
Then choose Separate by Selection

Now rotate it as you like....

Now is the tricky part....

I'm not sure how others do this, but I do it in this way...

suppose the uppermost cube is your plate and the lower one as your main ship...



Now we've separated these two in the previous step...
Now make them a single object by  Shift+RMB selecting each object, and then pressing  Ctrl+J ..... 



Now go to edit mode and go to vertex select mode... 
and press  B  to box select the plate from Orthographic View (Num 5) or a comfortable angle...

For yours it may be right side (Num 3)
then select all the edges to be joined....

In your case it's just two edge loops (Shift+Alt+RMB)....



Then press F to make faces between them...

Now, it mightn't be the best technique but I found it works for me...
Hope it helps :)