Yes, you have to be in DOS. I don't know what OS you're running, if XP you'll have to download a bootable floppy. Try bootdisc.com. If you do try the hotswap, remove and replace the original chip, just barely pressing it in to boot up the machine. If you have a chip extractor, that would help. It's hard to get them out without bending the pins. I've done these things myself, just be patient and careful, and you'll do fine.
Oh yeah, did you check out the boot block flash?