HWH can be a bear to get through to when they're busy but they will get back to you and when they do, they'll be very helpful. I had a few issues on my Suncruiser slides as well, which is one of the reasons I didn't really want hydraulic slides if I could help it. They may route you to a closer HWH service center. HWH has a 3 year warranty on their end of things so you don't have to go to your original dealer to get this covered.
Your coach is still operable. The slides and hydraulics work off a common reservoir and all of the various hydraulic lines run through a solenoid valve assembly on top of the HWH pump unit so they are all unique hydraulic circuits. If your only problem is with that one slide you can still use the rest and most certainly the levelling jacks. You may have to add some more hydraulic fluid to the reservoir if you lost too much but you can still operate the coach. Just don't touch the switch to the bad slide-out.
Been there, done that before.
As to your dealer not having time for you for 4 weeks when you just bought a new coach from him and now have an emergency - well I'd be on the phone to him pretty quick. I can understand being busy and scheduling that far out for minor issues but they have to have the ability to prioritize things according to the customer's needs and they're certainly not looking after yours.