Total resistance of circuit
If you're looking for Rth, you do exactly as you said (remove RL such that there is an open-circuit between A and B, then shut V2 off and measure equivalent resistance from A to B).

First, remove the resistor and short V2. If you label nodes at this point, it will help you to redraw the circuit in a more typical fashion:



Convince yourself that that is true, and from there you should be golden :)