Gospel of Matthew Theme of Sin

According to Jesus, all humans are sinners. Yep, that means you, too. But don't worry. Matthew makes sure we know there's a Jesus for that. Turns out, Jesus isn't a fan of sinning—color us shocked!—and he's here to forgive all humans of their sins. He does it on an individual basis for some people (remember the paralytic from Chapter 9?), but everyone else can be included, too, as long as they do what Jesus says.

1. Does Matthew's Gospel create any sort of hierarchy of sins? Are certain sins worse than others or is a sinner just a sinner no matter what? 
2. People accuse Jesus of hanging out with sinners. Who are these people and why does he spend so much time with them?
3. Are any of the disciples guilty of sinning?