When uninstalling your current manager, press triangle to view its information. Make sure you are in the MB, and not the GB. If everything looks okay you can remove without game loss. If for some reason it says xxxgb, stay away until all games are moved from int. to ext.
To do this you would have to run more that one manager (answers aone of your Q). OPM 1.7 does not have the option to move game files back and forth from int. and ext. and visa versa. I have tried them all, with every jailbreak device imaginable.
OPM 2.1D, has to be D (GAMEZ FOLDER)
Gaia, but not 1.03, chose the one below it. ( FT?? SOMETHING FOLDER)
Multimanager v10 w/ covers (GAMES FOLDER)
Run OPM 2.1d and multimanager v10... 90 percent backup rate
GOOD LUCK, hope this helps. If I deserve it please don't hesitate to +rep me, THX