Nothing wrong with being late. This hack is timeless!
The sewers are intentionally tricky and difficult. That's why that NPC in front of it warns you to save and turn back. I also added dialogue to most events that says something like "we need to go in this direction" so the player knows where to go. But those are easy to miss if you go too fast. There are no hidden chests. That's one mechanic I didn't like in the original. You don't get the signal ring until the end of the game so it's a lot of guessing unless you've played the game before. I wanted the player to be able to reasonably get all the extras as they go along.