It might be possible to fix it in Lightwave, there's 2 options with that prog, if the whole model has been made double sided then it should be possible to select all the surfaces and use the surface editor to make everything single sided again, since LW uses it's surface editor to determine whether a poly is single or double sided, if that doesn't work there's a plugin that selects just double sided polys, I think it only selects one side of them, and then they can be deleted.

If you want me to take a look at it PM me and we'll work something out that way.

Cheers

Billy