I just replaced my OVP a couple of days ago...
You do not have to remove the battery to get to the panel.
You should see a black slightly-contoured plastic panel about the size of the battery located directly behind the battery. It is held in place vertically by the firewall lip just below the rubber/foam hood seal. There are no fasteners, so just a gentle push down should get the panel below the lip, and then you can pull it out of the way.
There you will see a number of electrical components. The one you want to look for is a silver rectangular box (about the height of your index finger). On early models, it has a red top with a clear cover and an AN-type fuse recessed inside. On mine (93 and later), the top of the OVP is white. The fuse is either 10 or 15 amps. Check to see if the fuse is blown first and replace before you decide to replace the OVP.
The OVP has a bracket that is bolted on sideways to some other hardware. As far as installation is concerned, I found it easier to remove the battery first, so there was room to work with tools. Took about 10 minutes for the whole job, including battery removal and reinstall.
I don't believe the OVP has anything to do with the fuel smell you've encountered though. That's a fuel mixture problem. The OVP's job is to protect the vehicle's sensitive computer circuitry from voltage surges (such as jump-starting).
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car