I would think what you did is technically not allowed, but in practice, some/many Genius Bar reps might suggest that... and I guess there's no way Apple knows otherwise (for certain anyway... at this point).
Also, AFAIK, you can't add AppleCare anymore after the device warranty expires (after 1...
I haven't tried any DIY nor 3rd party iPhone/iPad repairs myself (and probably never will... even though I do some DIY for many other things, including laptops, TVs in the past, even violins/violas, etc), but this is pretty lame of Apple...