Was just on the phone with a Sound Devices service rep inquiring about warranty on one of their branded SD cards whose plastic write-enable tab is missing, and got some info to share with owners of original Mixpre 3,6,10.
(the card? My vendor, Location Sound said to send it to them [LS]for replacement!)
If you are planning on getting maintenance on your original MixPre, it's the best deal now.
They are entering the phase of legacy products where it will be harder and more costly to get parts and find someone who knows how to fix them.
The best way to go about getting service is to contact them before shipping the product to them, and pre-authorize a certain amount of parts cost so they can just open it up once and fix it.
Prices start around $200, you'll probably want to authorize up to $150 in parts to save them having to contact you with the exact estimate.