Hi Barbara
The price seems about right, I charge £125 for a three peice suite (3 seater + 2 arm chairs) but price higher if just the one chair and an awquard one too.
As for using HWE, should be fine, if the label says not to over wet it sugest that you can wet clean it, but would make sure, before starting identify the material and always test for coulor fast,
The main prob seems to be the electric, obviously unplug it first sounds daft but an easy mistake to make, my advice if using a T/M use a Dri Master from Hydramaster the best tool for upholstery runs water over the surface instead of spraying every where, if not try to use a tool with the jets inside, reduces the risk of overspray and keep your pressure low plenty of drying equipment, and make sure it's dry before the custy uses it.
Job done anouther happy custy
James