I would avoid using the converter software if at all possible, it has a tendency to either add to many details or not enough depending on what you want to do, best avoided.
Anyway the fact you have the Lavatronics (I presume backup?) firmware on there means you'll have had most of the hard work done for you already, should just be a case of heading into the OScam webif and typing in a few details, clicking save and probably restart and away you go.
First question to point you in the right direction on this is do you know when the Lavatronics firmware is from roughly? If it's the latest one it'll have a video intro, if it's an older one it'll have a static bootlogo but should also give some kind of indication when it's from, once we know that it should be a couple of minutes job to get you going provided no OScam files have been touched or edited already.