Can I boot up from external HD after replacing the internal HD?

I just ordered and received a new 500 gb internal HD to replace the tiny 80 gb in my MBP. I did not purchase an enclosure or cable to clone my computer on the new HD before replacing it. Can I just use SuperDuper to create a clone on my external HD, make the internal switch, and boot from the external drive using USB 2.0? If so, once booted, how do I transfer the clone onto the new internal HD so that it runs as before? Sorry if this is a really basic question, but I just don't want to physically make the switch without being able to have the computer functional with software. Thanks for the help.