For the $150 they replace the 450 with a 550. I just did that. Originally I replaced the screen and everything was fine for about a month, then went flaky again. Rather than mess around, I paid the money and got a 550 out of the deal. I am like you, I have gotten so used to using it all the time it is very strange not having it on there!
That's weird. A month or two ago I emailed them and asked about an upgrade path from the 450 to something else and they said there was none, and also that there was no repair option either. The gist was to "just throw it in the garbage." I'm glad I didn't do that, as after about a month of use mine is working like new after jury-rigging the small cable onto the motherboard with masking tape and foam rubber after breaking the clip.