+1 on running a new relay, fuse & wiring for the new lights.
The OEM wiring is only like 18ga or something tiny... I'd suggest 14ga for up to 100w lights... maybe even 12ga if the mood hit me.
You'll want to use a 30/40 amp relay and probably a 15a to 20a fuse, whatever came with the lights... I don't recommend increasing the fuse, that's asking for a fire
If you're looking to use the OEM fog switch to run the lights, I make a conversion kit for oem switches to control aftermarket or oem lights that bypasses all the oem wiring.