Is there a way to change what it does in holster mode? Because sometimes I'd like it to ring and such.

Menu, Profiles, Advanced.
Highlight a profile, Menu, Edit.
Select an event type, then you can pick what to do in and out of the holster.

I accidently messed up my Normal profile, so could someone tell me the default settings for Messages [blackberry.net email], MMS, Phone, and SMS Text? Thank you! :D

So, since the Pearl doesn't come with a holster, what is the holster mode in the settings?

The Pearl has a magnetic switch in it while holsters made for the Pearl include a magnet as part of the casing. When you holster your phone, it can auto lock itself based on your settings. It can also behave differently in response to events than when it's out of the holster.