Adding drive after install

My first machine is acting up probably because of my IDE cables or drives. I can install on a small 6 gig hard drive. Then I can remove my cdrom and attach an 80 gig.

What I would like to do is have swap and /usr/obj on the small drive and put the rest of my system on the 80 gig.

Can I simply transfer these slices and make adjustment in fstab?
Sure. There's an entry in the FAQ about this, titled "How can I add my new hard disk to my FreeBSD system?"