Get yourself a 4 gig SD card and copy the data off the original card on to it [don't delete it from the original card] so you have a back up copy just in case DME 2 doesn't know how to do it, or stuffs up doing it.
You won't lose your data from the original machine, and new data will continue to be logged on the same SD card as the original [or copy of the original].
If you use Sleepyhead to read your own data you will see that it records all the machine ID details, it will also show the date you swapped over to the new machine, plus all the ID information and details of the new one.
I have just done exactly this when I returned my loan Dreamstation and purchased a brand new one and had it set up as an exact clone of the loan unit.
The clinic let me keep the SD card from the loan machine [but I had copied the card files to a second one just in case].
All the data is still on the card from the first machine, and it has logged the swap over to the new machine and still continues to record all the data.
I download from the SD card to my computer every few days via the Sleepyhead program, the full data log right back to day one of CPAP use is there for me to view any time.. and it shows my compliance data averages combined from both machines, so no problems for supplying the information to ensure I keep my driving licence intact.