no grey tank on that model, unless a PO retrofitted it.
There is a 13 gallon black tank, sitting under the toilet. the toilet is the only thing that feeds that tank.
the sink and shower drains terminate under the black tank dump valve, so there is nothing to hold that water back. it'll just drain out onto the ground.
solution: blue tote-tank. you can hook that up to the sewer outlet, either with a slinky, or w/ a 5/8ths garden hose. There should be a "cap" that covers up the sewer outlet...most often, these have a 5/8ths threaded fitting on them, to which you can connect a short length of garden hose. the other end goes to the tote tank, which also has a 5/8th fitting. You can buy an RV grey water hose for 50 bucks,
or for $3.95, pick up a 6-foot standard washing machine hose at home depot. (has female fittings on both ends). When the blue tank fills up, you disconnect, and drag that over to the dump station.
inbound water: there is a 44 gallon fresh water storage tank under the floor in the galley. Water from this tank will feed the supply lines in the trailer by means of an electric pump. When the pump is activated, it should pressurize the lines, and when full pressure is reached, it should sense this, and shut off. it will turn on when the pressure drops below a set point.
If you have city water available, all you have to do is connect it to the fitting by the street-side rear corner, and turn on the water. the city pressure will pressurize the lines in the trailer. there is a check valve at either end of the system, one just inside where the city water connects, and one between the pump and the water tank, which keeps both sources from pushing water out the other end. (without these check-valves, city water would fill and overflow the storage tank...or water from the storage tank would be pumped out the back end of the trailer by the water pump.).
There are low-point drain valves located under the galley sink, and under the bathroom vanity. (one each for hot and cold lines). Under the galley, there is a 3rd valve for draining the fresh water tank. make sure these are all closed before turning on the water, or it'll just run right out onto the ground.
now. that's the way its SUPPOSED to work. How it really works...well, depends on what condition things are in, and what the PO has done to modify things. I've seen some here suggest testing water lines with compressed air, before connecting water to them. that way, if there is a leak, there won't be a mess. You can get a blow-out plug from your local RV place, which simply screws into the water connector, and connect a compressor to that. (less than 30 PSI, though!!). close all the faucets and drain valves, apply a little pressure, and go inside and listen for leaks.