Oracle newbie!! - Please help!!

Please bear with me. I am a complete newbie that has been thrown into the position as a Oracle DBA (lucky me). Anyways, we have a SQL Server 7.0 database that we need to migrate over to Oracle 8i. We have Oracle 8i version 8.0.5 installed on the same machine as the SQL Server machine. I tried to download and install the Oracle® Migration Workbench for MS SQL Server 7.0 software in order to migrate the database. Well, I read most of the release notes and I have to have the 8.1.5 client installed on the machine that I want to install this software on. Do I have to upgrade my Oracle 8.0.5 install to the 8.1.5 install? I have tried to install the 8.1.5 Enterprise Edition software over the 8.0.5 install, but I can't because the release notes state I can't install over a HOME (whatever the hell a home is - I still don't really understand this concept yet fully) that already exists. So what do I do? Do I have to uninstall the 8.0.5 software? I am afraid to do this cause I totally screwed up our NT server when I did this before. Should I just forget the DEFAULT_HOME that exists and install into a new home and completely forget the original home I created with the 8.0.5 install (which looks like it will waste a lot of disk space if I do this). What do I do!?!?! Any information will be greatly appreciated. Also, is there content on the net or a good book that will help me as a newbie? I recently got the "Oracle 8i DBA Handbook" from the Oracle Press. Is this good enough?

ALSO: Direct responses to my email address listed below will be greatly appreciated too.