In addition to the links off the mozilla-zine post, a "quick & dirty"
guide to updating seamonkey 1.1.x to 2.0.x and preserving info like
bookmarks, saved passwords and other settings ...
you want to
a) create new profiles for seamonkey2 and
b) migrate the old ones over.
seamonkey -migrate -P <new_profile>
(and exit it)
Run it again, it will ask you WHICH old profile you want to migrate.
Repeat for all profiles.
Once you're done, edit whatever means you use to start seamonkey with
a profile to look like
seamonkey -P profile
seamonkey -no-remote -P profile