I have an active location covering my quest card…I have the adequate number of progress tokens but had not yet killed the hill troll…I traveled to a location….which is still active…during the combat phase, I killed the hill troll….do I leave the active location there and advance to the next stage of the quest or do I have to complete the active location BEFORE advancing to the next stage of the quest…?

I'm going to paraphrase you just so I make sure I understand what you're saying…

Stage 1B of JdtA. You have more than 8 progress tokens on the quest card, but the Hill Troll is still in play so you can't advance to stage 2. There is an active location in play.

In the combat phase, you kill the Hill Troll. The question is: do you have to complete the current active location before going on to stage 2?

Answer: Immediately advance to stage 2, and the current active location remains in play. You do not have to complete the active location before progressing on to stage 2. On the next turn, any progress tokens won during questing phase (or otherwise) will be placed on that active location before you can place tokens on the quest card, as per usual.