Well,
Start with asking the guild stuff. Ask who are trusteable guilds/people to buy zhelms from.
We are here to help you ^^
This way you will learn stuff and you won't have to ask it again. Just be carefull who you trade and what you trade.
Always get a second opinion when planning to spend a big amount of money (10m+)
There are a lot of maplers out there exploiting people like you that don't know the game quite well yet.
Some sites for you to take a look at:
Basilmarket
Mapletip
Get yourself an account at basilmarket. You can place topics there and ask maplestuff. It has always helped me a lot!
I don't use mapletip myself, but it also has a forum, I prefer basilmarket's forum though, and i think the database is more up-to-date then hidden-street's one although I think hidden-street is more user friendly.
It's all up to you what sites you will use, but I really do recommend Basilmarket. It's really user friendly easy to use and I always got help there.
Good luck on checking the sites,
Greetings,
Simon (xEdWiNeMx)