But don't expect big, whopping rewards and parades even if you do manage to get it to succeed.

Once negotitations are over, you can go back and report it to Lt. You'll know it worked, if you can go back to Vogga and have him acknowledge that Goto's yacht has been destroyed. I've managed to complete the mission in some playthroughs and not in others. The trouble is that like so many things in TSL, the mission is bugged, and the conversation where you negotiate with Vogga (with varying degrees on success, depending on your negotation skills) doesn't always trigger. Now, once you've been to Goto's yacht (part of the main plot), you should be able to go back to Vogga and negotiate a deal to get him to deliver fuel from Sleheyron to Telos after you've gotten Goto's attacks on his ships stopped. Once you reach Nar Shaddaa, you can take the matter up with Vogga, who insists you must deal with Goto for him first, before he'll make a deal. Grenn on Telos, because Citadel Station lacks fuel after the destruction of Peragus (but you know all that). Also, the fuel quest itself is frequently bugged.