It's been a while, but i'll give it a try. first off vapor or liquid withdrawl @ the tank probably liquid on anything but an air cooled engine. the tank outlet should be permanently marked, while your at the tank look for an automatic overpressure relief valve, lp pressure changes with temp(huge changes like 250 psi) next a filter that rarely needs service, then a safety switch usually electricly actuated(ignition sw) but it uses a vacuum signal from the intake to trigger it (if the engine doesnt crank,you get no lp) next a vaporizer/regulator sometimes combined sometimes seperate, vaporizer uses engine coolant to help vaporize the lp, (basic refrigeration, the liquid to gas process has a cooling effect,) the coolant even at low temp. 30/40 f is still warmer and more efficient at exchanging heat than the ambient air is, next the pressure regulator usually has an adjustable preset and vacuum signal line that increasespressure as the engine requires more fuel and finally the carburator to meter the fuel and air.
Try to identify all of your individual components and their make and model then go online and get the paperwork for specific information, also check with the engine manufacterer if it is a factory install they will have spent lots of time and money to optimize the system and their service information is as good as you can get especially if you can access the updated electronic service database.
My experience (forklift/industrial engines)is that their are many lp component manufacturers and the systems that work best are hybred systems assembled by the engine builder/converter, you typically lose about 10%power with lp over gas but if you are bold and careful ignition timing adjustments can help to compensate some.
Caution a liquid leak is going to cause severe cold injuries and the vapors are extreemly flamable/explosive.
try to find someone to help you become familiar with your system before you try to service it yourself, an old time forklift mechanic would be a good place to start.
I hope this is helpful information