Converting a major site

***info***
Website: dev.300mclub.org
Drupal: v6.x
Forums: phpbb2, phpbb3
Modules: Media Wiki, Search
Mods: none
Theme: CrystalXL
PHP familiarity: Low

Okay, I've never installed Drupal or used it before, so I'm unfamiliar with some things I need to do. Here's the scoop: I'm converting a large site (www.300mclub.org) to Drupal manually right now. There is a sizable phpbb forum and a whack-load of content that needs to be moved over. I do have a few questions in regards to porting features of Drupal and moving php sites into Drupal.

- I will be running a phpbb3 site that I need to port into Drupal. I've done some searching and haven't really found a clear answer to linking the forum into the CMS. I'm not that well versed in php so I can't use a solution that requires a lot of knowledge. My biggest issue is that I need continuity between Drupal and phpbb. They will need to use the same user DB and when a user logs into Drupal they need to be able to click on the "forums" link and it will automatically move over to their forums account with reflective permissions. Is this at all possible?

- Along the same lines as above, can I import user information into my Drupal users from my existing phpbb accounts? Would an import of the mysql user table from one to the other work?

- The site has a lot of pre-existing php pages that are used to display and administer the list of members. Is Drupal code friendly enough that I can copy-paste the php code into a "page" in Drupal and the information will remain? I get the impression that this section may have to remain a separate part of the website.

Thanks for the help in advance. I'm not an advanced php user but I have a lot of experience with HTML and such.