If you can find the make of the stovetop/oven, there should be a manual on the "Tools" tab at the top of any forum page, then "Manuals" "appliances" and "ovens" in the submenus.
The lighting procedure for the ovens can be very tricky, even if you have done it before. Have a butane long probe lighter at the ready, open the oven door, put the oven control in the "Pilot" position, press in and HOLD the oven control FOR A FULL 60 SECONDS before attempting to light the pilot while still holding IN the oven control knob. It seems to take a LONG time for the gas to get flowing to the pilot, and since it flows so little propane, there is little danger in waiting 60 seconds before trying lighting. Once you see or hear the pilot flame lit, CONTINUE HOLDING IN THE OVEN CONTROL KNOB FOR ANOTHER 60 SECONDS. The pilot sensor bulb needs to heat up sufficiently to keep the pilot flame going on its own. If you let go of the knob too soon in any step, you get to start all over from the beginning.
Frankly, I use a tabletop electric convection oven/broiler/rotisserie instead of the gas oven.
If it were me, I might keep trying to get the water heater lit on propane maybe 10 to 20 times before I give up on it. There may be a lot of air in the propane line to the heater, and each attempt to light will not purge much of that air for the pilot light. Also listen very carefully when you attempt to light the water heater. You should be able to hear the electric sparking noises as the water heater attempts to light. I hear that with my Suburban water heater if I listen closely. Also, you might check the 12 volt fuses to see if possibly the 12 volt line to the water heater that generates the sparks, and controls the gas flow valve is there.
Either Heartland service your your selling dealer should have the info on your dump valve handle for your model. If you call Heartland service, have your VIN available for things, as that is the way the files are kept.
Remember that you paid a substantial portion of your purchase price towards warranty repairs, and that Heartland will allow you to get warranty service from any RV servicer you choose, with prior authorization from them. If you can find an independent RV servicer (no RV sales) you will most likely get better service. Heartland keeps lists of independent servicers they have worked with in your area, or you could look at RVServiceReviews.com.