There may be a few ways to get this working, but its hard to say with out seeing what's actually going on.
First, Back up your tangos immediately. Make sure you have a copy of them in their current state seperate from the one you are about to edit.
Second, Edit the copy. Second Life comes with a handy dandy feature in the build menu called, "Undo." You can use this feature by using ctrl + Z (or apple + Z if you're on a mac) to move any prims you may have moved back into their original state. (You may have to do this a few times depending on how much you move the prim to tweak it. Becareful though, Undo only goes so far.)
Third, If you start tearing apart the Tango breasts piece by piece you'll see that there are actually many layers to it. Using the "Select Face" and "Edit Linked" features in the build menu at the same time you can pull the breasts and their corrosponding pieces apart by moving them out of the way, off to the side, ect. If I can remember right, there's a tank top layer, a bikini layer, a nipple layer, and the actual breasts themselves. Please keep in mind that these are the only layers you're going to have for them.
Fourth, You can (without using the hud or scripts supplied) get these textures to show up by going into textures (in the build menu tabs) and changing the transparency to 0% instead of 100. With this you may be able to layer the pieces that you want appropriately.
The Problem: Second Life Alpha Textures glitch like mad on mesh. Currently there is no fix for this. So the corset that you're wearing that might show your nipples might only show half of them because the alphas glitch.
Unfortunately, this is about all the help I can offer. x.x I hope it wasn't too confusing!!