I managed to replace upper case on a MacBook Air using this excellent manual from iFixit and saved about 400€. I though it would be hard, but since everything is integrated, I found it quite easy. The downside is that replacement parts are quite expensive.
I had a SIM card error on my Nokia N900 phone. It started happening last week, just before going to FOSDEM conference (during the same week I also managed to spill a bottle of water on my laptop and the screen stopped working;)
The error message read “All telephony functions, including emergency calls, are disabled due to a communication error. To recover, you might have to reboot the device”. I knew it was a hardware problem and I thought it’s the end of my favourite phone. Luckily I found this link: http://talk.maemo.org/showthread.php?p=1154781#post1154781. I put parts of a paper clip between GSM module and its shield using adhesive tape and it fixed the problem! I feel proud of myself;)