i need help, please

Please, I need help.
I was in halo, and then a message appears and it said something like “load old saves” and “load new saves” I accidentally put new saves, so I lost all my saves and everything. But, the saves, my statistics, and everything it’s still in the xbox, I went to “game management” and I have there 40MB of saved data, so…its there, but I dont know how to do to charge the old saves, to recover everything.

The xbox support said that I must delete the game and reinstall the game, and then i will recover everything. Is true?, I bought the game online, in the live, I am afraid to lose the game and have to pay again, That will not happen, no?