I assume this is the ONAN 3600LP ?
You will need to remove the generator (almost for certain and it will make all the work easier) and then remove the shroud that covers it.
'03 Ram 2500 CTD, 5.9HO six speed PacBrake std cab long bed Leer top and 2008 Bigfoot 25B21RB.. Previously, 2008 Thor Freedom Spirit 180, SOLD! 2007 Winnebago View 23H Motorhome, SOLD!