Back up the donor game, and on the SD card you'll find the target game's save files as well. Replace the file you wanted to restore and go back to Checkpoint.
Probably the best source currently is the "LayeredFS Title Compatibility List" at awesome-table (google that) by Crownfox (GBAtemp member). I'm a newbie, cannot provide a direct link.
With regards to option 1: I updated without blowing fuses to 5.1.0, so the system is only downloading the exFAT update. Can I still somehow make it work (I've got the original 5.1.0 update on my computer already of course)? I moved the update files from SYSTEM\Contents\placehld, but I'm not sure...
I get what they were trying to say but what the ad actually says is "we tried to cram a ton of features into the iPad but all of them got irreparably mangled
in the process."