RE: electric to nitro.
Is the bipe designed to be glow powered? If so, the instructions will hopefully have a lot of detail on setting everything up. If not maybe consider downloading the manual for a kit intended to be glow powered. Something like a trainer will have a lot of detailed tips and instructions. You can download most of the kit manuals from Great Planes.
Like the others have said, it is basically just a matter of having a strong firewall, fuel proofing the area and plumbing the fuel system correctly. Some airplanes intended for electric only can be very light and fragile so be careful. If it is designed for either power source then you'll be OK without much stengthening.