In order to reach LEO, a fully loaded shuttle needs all the fuel in that large external tank, plus two solid fuel boosters.
As I pointed out in an earlier post, you need about 2.2 km/sec of delta v to enter a trans-lunar orbit from LEO. Even if the entirety of the cargo capacity of the shuttle was extra fuel, the SSME's wouldn't be capable of getting the shuttle up to this speed.
Once at the Moon, your shuttle would be moving ~ 0.8 km/sec slower than the Moon, and would need to do another burn in order to be able match speeds and enter orbit around it.
Then to return, another burn is needed to re-enter another trans-lunar orbit in order to get back to Earth. Once back, the shuttle will be moving at ~2.2 km/sec more than LEO orbital speed. The shuttle can't hit the atmosphere at this speed, so it will need to do another burn to shed enough for re-entry.
So, this works out to at least 6 km/sec total delta v for the trip. This jumps the fuel requirements to 2.8 times the mass of the empty shuttle. Adding a lander would increase this fuel requirement. (some thing the equivalent of the Apollo LEM, would require ~20% more fuel.
A good part of the Shuttle's mass is there for re-entry and landing, and would be dead weight as far as the majority of the trip is concerned, so you'd be burning a lot of fuel to get something to the Moon that is of no use when you get there.