You may disable the existing converter by turning off the breaker that feeds is IF the breaker feeds ONLY it, Else there are other ways.
OR, as I did on my Xantrex.. You can disable the charger module (I think yours ships that way, see my earlier post) and continue to use the factory converter.
I did this because I really like the factory converter in my Rig (Progressive Dynamics Intella-power 9180 with optional wizard installed, No better converter have I ever found, though Xantrex inverters.... Well, I'd say the same about their charger modules but for different reasons and I PERSONALLY (not professionally) like the Wizard a bit better,, "Profesionally" (I am a trained and certified electronics technician even if I never worked in that field) I would have to say they are equal.. Both are 3-Stage plus.. it is the Plus that is different, also the Xantrex is programmable and the Wizard is not, but the Wiz is factory programmed for the batteries I have so programmability does not matter (the Xantrex is too).