A quick keyboard clean up can be attempted without having to take the Pre apart. To get started have a look at the image in the link below:
palm-pre-keyboard-removal-1 | Flickr - Photo Sharing!
To begin with slide out the keyboard of the Pre then carefully insert a paper cutter or any sharp edged object between the keyboard(kb) bezel and the Pre's case lining, you can lift up the kb bezel. Once lifted you can run a fingernail under its edge to pry up the rest of the kb bezel. It has two small clip inserts on both sides which will release quite easily.
As you start to lift up the bezel you can see or even hear it coming away from the lower layers as they stick together with an adhesive surface. You can have a quick look inside to see if the surfaces are clean. Check for any lint or dirt nested on any of the surfaces which might prevent the physical key outside from completely pressing on the inner surfaces.
If it looks all clean here the next step would be to look under the white layer which you will still see stuck to the bottom of the case under which you have the keyboard contact points. In order to peel away this white adhesive layer you could start with one of the corners. Pry it away with the cutter and then use your fingers to carefully peel it away. Just have a look inside to check if all the contact points are clean.
Once done put the white layer back in place, followed by the bezel and with a little pressure you could clip everything back into place.
Remember, you are not disassembling, you are just lifting the bezel and the lower layers away from the lower edge. The upper edge remains in contact. Do take the necessary precautions of working carefully with the cutter and peeling off sticky surfaces slowly. Operate in a dust and static free environment (I don't mean an isolated chip assembly lab standard but reasonably clean with you not carrying static to fry the inner circuits on contact).
There are a number of threads here as well as articles on other websites (Google) which could walk you through the steps of a full disassembly in case this does not work and you want to opt for DIY keyboard replacement.
I used the above steps to remove a human hair which had managed to slip in and was resulting in erratic behavior of one key.