I would do but since its soft modded now its a no go.
beg to differ unless you have an extremley pants softmod.
most softmods install a shadow C drive which hides any dodgy content you may have on your xbox.
simply start up your machine with the original game you want to play on live in the drive and it will 'cold boot' your machine. Basically your machine will auto boot to the game and the softmod will never kick in - therefore your machine will be safe to play online.
My xbox has been softmodded for about 2 years now and it works a charm online.
which softmod do you have??
If its blackwars or krayzies then you will DEFFO be ok if you coldboot your machine.