Worried about ruining more than the warranty of your Apple TV whilst trying the DIY hard drive upgrade? Then why risk getting your hands dirty - TechRestore and MacService are more than happy to take care of the heavy lifting for you. Both companies have recently debuted overnight Apple TV hard drive upgrade services that begin with 60GB drives and go all the way up to 160GB. While both companies are fairly hush-hush about what this service does to your warranty (hint: say your goodbyes before shipping the device off), the good news is that drives they install do carry warranties of 3-5 years.
Looking through the two services reveals some interesting differences. First, MacService more or less offers all-inclusive packages - overnight shipping through and through, with a single list of prices laid out to keep things simple. TechRestore, on the other hand, offers a couple of shipping options and seems to be slightly cheaper (especially when choosing the full overnight option) in price, though I've never had experience with either company to see if 'you pay for what you get' (a Dave Matthews twist on the ol' adage) holds true.
Both services are live and kicking, so feel free to comment on your experience if you take advantage of the upgrade.