21 y/o needing advice over index/mutual funds.

[Woolygimp]

I'm 21 years old and am looking to invest $5-$10,000 a month, but I'm not interested in trying to become a self learned stock broker at the moment. I'd rather let people who know what they are doing do the investing for me in the form of index or mutual funds.

However I have a few questions regarding how I should proceed.

Do mutual funds have any advantages over index funds, or vice versa? Do you prefer one over the other?

Would you recommend diversifying and purchasing both?

Should I purchase several different mutual funds?

Which online trading site would you recommend to build my portfolio?

Thanks in advance for answering these questions, and if you have any other tips they'd be appreciated as well.