You don't need to call tech support to enter a key value in. It's as simple as entering the code exactly as it appears on your computer screen. The user interface for entering letters and numbers might have been a bit complex with the x36 line, but it's not something that should stop you in your tracks.
The user manual for the SDS appears to indicate that they have modified the UI for that part of things anyway - I recall seeing instructions for something that showed using the soft keys to move left and right, instead of 4 and 6.
Having said all that, if there is some reason that you absolutely cannot handle entering a key value, yes, there are shops like Scanner Master that will do it for you, but you will pay for that work.
Even if it uses a completely separate version of Sentinel, there's no reason you would have to redo it all. You can export from one version of Sentinel and import that into another. I do this all the time between my HP-1's and my x36's. I maintain the one set of favorites lists on my x36 Sentinel, export them, and then import them into HP Sentinel.
I can't speak to whether or not you could swap the cards between the x36 and the SDS, but it would not work between the HP and the x36 as the file/folder structure is different. Even if you did get it to work, if you're swapping cards between two radios, that means one radio can't be used while its card is in the other radio. Just buy a bunch of cards and program them all for each different radio and use the import/export feature (If necessary) to keep your FLs the same across models.