In the Reflection line, the plumbing and AC prep is there - the outside vent hole has to be cut, but is marked. You DO NOT want a non-vented dryer unit dumping all that moisture into the rig. That said, RV washer-dryer units, especially the combos, are only capable of very small loads.
The brand-specific forums (in this case, the Grand Design Owners' Forum) is often a very good place to ask this type of question. Great bunch of folks over there.
Rob
U.S. Army retired
2020 Solitude 310GK-R
MORryde IS, disc brakes, solar, DP windows
(Previously in a Reflection 337RLS)
2012 F350 CC DRW Lariat 6.7
Full-time since 8/2015