The exhaust rusted away on my genset. I will have to replace the manifold because it rotted out above the flange that the muffler attaches to. Will I be able to do it with the unit in the motorhome or will it have to come out? If I have to pull it I will have to do it by taking it out from the back. It cannot be dropped through the bottom. Any suggestions on where to hook it to pull it or any suggestions on the whole procedure would be most helpful!