Information on the trade-in program is (was?) on the Airtronics website. I recommend calling Airtronics directly:

Global Services
Attn: Airtronics
18480 Bandilier Circle
Fountain Valley, CA 92708
TEL: 1-714-963-0329
Email: [email protected]
Fax: 714-964-6236

Here is the email I received when I asked the service department about the trade-in.

"Hi,

If you wanted to use the Airtronics trade-in program, you would need to go to our online web site and print-out the service forms. On the first page, you want to note "Request Airtronics trade-in program instead of repair." and list the replacement system you want. On the second page, you can list your billing information, and note if you want us to have the new system sent to the Fountain Valley Hobby People store instead of shipping it to your address. If we have it sent to the Fountain Valley Hobby People store for will-call, it will save you the shipping fees.

We have to process the Airtronics service requests through our computer systems, so when we receive the unit from the store, it may take a few days before the new replacement unit would be available at the Fountain Valley store for pick-up.
Thank you,
Airtronics Service

Airtronics Service Dept.
18480 Bandilier Cir
Fountain Valley, CA 92708
714-964-0827 ext 1327
M-F 7:00am to 11:00am Pacific time"