What precautions should I take in paying a photographer for my son's wedding CD?

The photographer is too far away for me to go pay him and pick it up in person so it will have to be mailed. He wants to be paid in full before he mails it. I asked him to e-mail me a bill of sale stating what it is that he is selling me, the price, when I can expect to recieve it (a time limit for him to ship with-in) and the address for me to mail payment to. I have not received anything from him even though he stated he would do that the afternoon that we spoke. It has been four days since then. I think he thought it shouldn't be necessary for him to send that to me. He seemed as if I should just send him a check and he would mail the disk. The wedding was 4 months ago and he may be a little put out with us because we have taken so long to decide if we wanted to buy prints or the disk, so I am just a little worried that if I just mail him the check, he will drag his feet in mailing it. ( He was paid a required fee before the wedding).
Any advice?

All you can do it trust.

Maybe you could call him and ask if he could send it priority mail. Tell him you will add the extra fee for this mailing should be no more that $5.00 additional but that way it will have a tracking number to follow up with should it get lost.
Priority mail once mailed will take 3 days tops. If you are closer to him probably only 1 day.

He will mail it. If the pictures were lost and he doesn't, then you can take legal action. More than likely though he just wants to make sure that he gets paid.
That's definitely bad business on his part. Immediately after shooting a wedding, I email a couple of the best to the mother of the bride, or a good friend so that they can post pictures right away for those that were unable to attend the wedding.
It seriously would not kill him to make a bill of sale! That's really tacky and lazy of him not too.

Make sure that you get a copyright release with the disc though so you won't have any trouble printing them.