You can upgrade Troll to level 4 with troll hides and bone fragments, not sure where iron or obsidian comes into the picture.

Yeah, you can do the swamp in Troll armor of any level. Just realize you're a little more squishy and your strength is mobility. Always be aware of your surroundings, keep your food up, avoid getting the attention of too many mobs at once, you'll be alright. Don't go in the swamp at night at this stage, that's asking for trouble.