ORIGINAL: goirish
How do you know what voltage you can use--I don't see anything on the ESC. It is currently using a 9.6 NiCD I have a 11.1 LiPo
Yup you are well within the margin of safety with the ESC.
If it comes with a 9.6 NiCD, you can typically use an 11.1v LiPo. The Lipo runs less than 11.1v when under load, so 1v is not going to make a big difference in terms of the ESC, but it will make a difference on how the plane performs in the air.
That will be the only thing you have to do.