Where did you buy this MacBook from? I was not aware that Apple offered a $99 ProCare plan. That sounds like another company altogether. Maybe they could no offer advice because they had no advice to give. Anyway, moving on.
By far the fastest way to move all your required stuff from one machine to the other is via Ethernet. That was one connectivity protocol that you didn't mention. If the Gateway has ethernet, great. If not, go slap $15 at BestBuy and get one and install it.
With ethernet in both machines, all you need is a cross-over ethernet cable and a little patience. Connect the machines together, share the My Documents folder and put everything you want to move into it. Suck it off with the MacBook.
A slower way, but just as effective, is with a large capacity USB flash drive.
A really slow way is to make CD's over your stuff and transfer it that way.
Remember, the Office program that came with the Mac is only a TRIAL and will expire in 30 days from first use. You will need to purchase a real copy of Office 2004 for Mac to continue to use it. Student & Teacher edition is around $130
I just went out last night and bought the new MacBook base model. After plunking down $1800+ once all the additional stuff was added in, I asked what I thought was a pretty straighforward question, which was,
"Now that I'm switching from PC to Mac, how do I get all my stuff (files) from one to the other?"
Seemed like a pretty reasonable question (again in light of the fact that I had just dropped $1800 in the space of about 4 1/2 minutes) but the guys refused to give me any ideas unless I signed up for the $99 ProCare plan. I passed.
So, all I really care about moving are my Word, Excel, and Powerpoint files, some digital camera pictures, and my roughly 3000 songs. My existing PC is an old Gateway with a CD/RW drive, an old-school USB port, and a Firewire port I installed for my Ipod.