2 quick and probably easy(stupid) questions

[js9234]

I purchased a 2013 Springdale Keystone 294BHSSR and have two stupid questions. First, when you use the black tank and empty it do you completely empty it after a weekend of camping or do you refill it with a little water and chemicals or what? I know, stupid question. Second question, when using the hot water heater it says to make sure it has a certain amount of water in it(Suburban model) before lighting the tank. How do I know when it has water in it? I will have a third question later about my tow vehicle because I think I'm over my weight limit or close. I'll have to get all the specs on everything before I post but my info for now is a 2012 Ram Crew Cab with 3.55 gears and a max tow of 8500 lbs. I do have a 10,000 lb WDH and sway bar as well. I am a complete newbie with travel trailers. Never even been in one till I purchased this. Not new to towing but new to towing a travel trailer.