If the breaker is blown, it shouldn't cause any problems if there are no major problems causing the breaker to trip. The jumper wire must be able to carry the full amperage of the breaker rating (30 amps?).
Do you have ANY voltage measuring/testing device? DVM is best, 12 volt test lamp might work. You can't SEE voltage - you need an indicator.
You can call Heartland service at the phone # on the top left of the portal page. They just deal with their brand of RV's, not many brands like the dealer. They should be able to accurately tell you what breaker is for the slide. Always have your VIN # with you when you call Heartland service, so they can uniquely identify your rig.