The description I see in the '96 Owner's Manual I linked you to is consistent with the LP tank installed in my '95 rig....it says there are 4 valves total - one liquid fill, one overflow, and two vapor. The liquid fill valve has a covered connection for the fill hose and has a handle to rotate for opening & closing....there is no pressure regulator associated with the fill valve. Next to the fill valve (which is the largest valve) there is a small rectangular overflow valve which is made of nylon and has a small hole in the center....this is used during the refilling process as a safety backup to the automatic shutoff sensor in the refilling pump - if liquid starts to flow out of the overflow, that tells the operator to manually stop the refill process as the level of liquid has reached its' limit. On my rig I have two vapor outlet valves with associated pressure regulators attached in the downstream gas plumbing. One serves the house appliances (heater, water heater, refrigerator and stove) while the other serves the LP Generator. If your rig has a diesel generator, then you will have one less vapor circuit with a regulator.
So that's kind of the long answer.....but wait, there's more!
If you are restarting a previously dry system, there will be a need to "bleed" the trapped air out of your LP gas lines in order to get things working. This means that simply opening the vapor valve on the LP tank won't always ensure that the refrigerator or water heater will properly light off. Normally the last appliance on the delivery line will be the stove....which means that if you light a burner on the stove and you get a consistent blue flame, the rest of the system should be almost cleared of any remaining air. With the stove-top burner still running you should then be able to switch the refrigerator to LP mode with one or two attempts before it will consistently light off, the same goes for the water heater and the furnace - each of those other appliances will have a short branch off the main gas line that could still have a little air left to bleed off.
If your rig has not been formally inspected or serviced for a long time, you should seriously consider investing in that expense to ensure that all installed systems are working correctly and safely - LP Gas in particular!