iPad 2 Wifi picks up, but fades quickly.

The iPad 2 wifi setup is pretty simple. It is just one flex cable that runs near the home key at the bottom of the iPad.

That being said your issue sounds like the small connector that attaches for wi-fi signal has probably come loose. (you can see it closely @ step 43)

Unfortunately it seems you are going to have to open your iPad. The guide you have chosen is the exact one that you need to be able to fix this issue.

I highly recommend caution, go slow, pay close attention to the notes in each step. There are flex cables that are easily broken during the removal of the front glass.

What I would do is open it up, get yourself to step 43, and check to see if that connection is secure. Most likely it has come out or isn't seated properly after your unfortunate drop.

Good luck!