beginning

こんにちはわたしはショーンです。はじめまして。どうぞよろしくおねがいします！

I would change it to 

はじめまして、わたしはショーンです。
よろしくおねがいします！

Hajimemashite means "it is the first time I meet you" so you don't need konnnichiwa here.

And it is also more common to say yoroshiku onegaishimasu than saying douzo yoroshiku onegaishimasu in this sitation, but I am not 100 percent sure on that.