What is the best way to handle this? How can we both ensure that we get what we've agreed to?
I'll add that the price is only a few hundred dollars, so expensive solutions are not relevant.
2. Escrow.com does a very nice job.
3. Be certain that the actual registration is transferred, which is more than the WhoIs record being updated.
4. Be certain to move the domain into an account over which you have exclusive control, not an account which is a sub-account of the seller.
That's a pretty good start for avoiding swindles.
Use the www.#*$! history tool (fee based) to research the ownership history of a domain. If you see a recent whois change, contact the old owner to see if he did indeed sell the domain. Many of the current scammers are just changign the phone number and email address on the whois info...making it look like the old owner just updated his info.