He could order a HD DVR on D* web site and it would have him setup an appointment for a new dish install.
Better though is to call Directv and ask about it, often you can get a deal depending on the history of the account. You should not have to pay more than $199 in almost any circumstance. But many have gotten $99 or less if they have a good history.
Remember the upgrade will require a 2 year contract, and will add $16 in fees to their bill each month ($10 for HD, $6 for DVR). The Plus HD-DVR package costs $73/mo, or $76 starting in march. This saves $1 off the plus package and required fees.
As for receiver, you'll get whatever is on the truck, but generally it is a HR21/22/23. Only difference is the hard drive and some minor tech specs that won't make much difference. HR22 & 23 have 500gb drives, the HR21 has 320.