Hi welcome to the forum.
I believe you'll find the 7KW will install in nearly the same space as a 5.5KW or the 6.5KW. it's only a dozen pounds heavier.
Onan sells the templet's you use to cut out the floor access panels for maint. and cooling. If your coach has the prep kit, transfer, isolated bay, it would be fairly straight forward. The exhaust tube and remote start, hr. meter are other options.
J & J
+ Kickr's the Vonderhund
, ES-38RSSA, 19.6K#
, 3500HD-Max, CC, 8'-DRW, 9.1K#