Multi Service Discounts & HDD Upgrades

Over the years I have had three Series 1 and 2 Tivos with lifetime service. When I went HD I purchased 2 HR 10-250's but have not had to pay any service fees to Tivo because I had the premium package with D*. All of the older Tivos are being used by my adult children, two in Florida and one in Georgia.

I am now considering getting an S3 (I have both D* and cable) and cutting back my D* service thus making the cable (Brighthouse in Central Florida) my primary TV service. Reading the Tivo website regarding multi service discounts, the lifetime subscriptions seem to qualify as a primary service so that the multi subscription rates would apply.

Does anyone have any advise as to how to go about claiming the multi subscription discount given my situation. If need be, I can probably borrow back a unit and cause it to call in from my home but, is that necessary? What info do I need to claim a discount?

On another front, if I buy an HD and later buy an S3 during the $200 rebate period do I have any problems with the discount? Also, if I upgrade the HDD in the S3 can I simply put the old HDD from the S3 into the HD without have to do any of the computer work need when upgrading a brand new HDD?

Any advise would be appreciated.