You could add some fresh gas, your going to have to add it sooner or later. The fuel filter is between the tank and that valve.
Since it's new to you and if you have no record of the filter being changed I would change it so you start fresh.
If you don't hear the fuel pump when the key is turned on (2 or3 seconds) then most likely the pump is inop so the thing to do then is see if you have 12v going to the pump.
John & Cathy R.
06 Pace Arrow 38L W24
08 Lincoln MKX AWD
See My RV Upgrades