You can save the game at the very start of ME3 and edit the save game so it reflects your past choices.
All you need is gibbed save editer and an extracting program.
For xbox you need a USB drive and a program that can extract, rehash and insert xbox files such as Horizon.
- you will need to save both your gamer profile and the character file you want to edit from the xbox HDD to the USB
- Use Horizon to extract the files from the USB to your pc in .xboxsav format (make back ups or a folder to hold the saves)
- Open the file you wish to change with ME3 gibbed, edit to your needs and save.
- Use horizon to replace/reinsert the edited save file on to the USB (must rehash files afterwards or xbox will not read the save)
- save gamer profile and the new edited save game back on to the xbox HDD
- If you have succeeded your xbox will open the file and play, if not take the files back to PC and trace your steps.
For PC it works the same way minus the back and forth with the USB.
This method can also be used to change/mod xbox/PC characters appearance, level, credits, reputation, paragon/renegade, backstory, love interests and previous choices without the genesis dlc. A prime example is giving a custom femshep the default femshep hair.
This method is relatively risk free, just be careful you DO NOT DELETE YOUR GAMER PROFILE at any point. If you have never used your gamer profile on xbox live or do not have a back up and delete it, it is gone for good. With regards to the file editing, in worst case scenarios the file simply wont load - as it is a new save with no value you have lost nothing important.
If there is a way to do this with PS3 i don't know how.
If you attempt this and find it doesn't work, feel free to contact me as i have typed this from memory and may have missed steps (fairly certain i havent).
Useful information;
http://forum.bioware...e3-info-thread/
http://forum.bioware...ate-14-05-2012/
Or even easier, download a save