authorizenet

I seem to recall a post a while back in which
someone was installing Authorizenet's software.

I am in the process of moving a client's web site from an
NT box over to either a FreesBSD or Linux box and need
to deal with the Authorizenet portion of this site.
Can anyone offer some guidance, or share their
experience with getting Authorizenet to work?

v/r
-Mike