by Kale » Mon Dec 29, 2014 7:11 am
You can either go back to an earlier save in chapter 3, or continue on without it. I don't recall that the gossip skill did all the much, apart from allowing you to complete Q63 "Slay the behemoth" in chapter 3. Other Thieves Guild quests rewards though, namely the persuasion, mercantile, etc. bonuses are a bit more important.
I'd recommend beating the game on your own first. Then you can decide if it's worth starting over following the walkthrough to the letter. That's ultimately your call either way.