former altar boy Mac tinkerer for a quarter-century
Ditto re: standoff screw
It's very important to clean and prep the terminals before attaching the new leads. Get rid of as much glue as possible and any stray solder that might be left from the un-soldering process. Make sure all three terminals are electrically isolated from their neighbors! Like the instructions tell you, leave no more than a nice little pinhead-sized dome of shiny solder on each terminal and no 'cold' solder connections, which have the characteristic DULL GRAY lustre. If you must--do them over or risk having to pop the dang thing open all over again!
Actually, the "button" side released fairly easily and I was able to loosen the top end with a plastic spudger. However, the remaining side was a @#!@! and the process of popping it off caused the protruding screw lug to break off the internal guide, which itself came off seconds later. Oof! While the side guide was easily glued back in, the lug ultimately became a casualty since it was too small and unweildy to SuperGlue™ back on. But, as Meat Loaf wisely sings, "two out of three ain't bad." The 'phone can live w/o one screw and possibly two if the center lug remains.