I imagine the hardware of the hp 49g+ is quite similar to that of the 50g. The enter key on my 50g went mushy, which is really annoying on an rpn/rpl calc where you're constantly mashing the thing. I asked for advice on this forum to fix the issue and successfully repaired my enter key with some glue and the advice in this thread - http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv019.cgi?read=171784 . Basically the post under the enter key and some of the other keys had punched clean through the foam backing that goes underneath the keyboard so they weren't getting the rebound that they were designed to. but on to how to open the calc...
To open the 50g up use a suction cup (you might need to moisten it to get maximum grip) to slowly pull the screen cover off, then find a small screwdriver to unscrew the screws behind the screen cover, then pull the two halves of the calculator apart with your hands (this is pretty hard, and will probably take a while.) Be careful not to pull it apart too hard or else you will break the wire that goes to your speaker, which is glued to the back cover of the calc. What I did was pull the speaker off the back cover so I could open the calc fully and lay it open. Then you need to unscrew a bunch of screws that go into the motherboard inside the calc, and use a drill bit to wear away the caps on the heat sticks (is that what they're called, the little plastic things that run through the motherboard to hold everything in position?). Once you've done this properly, you'll be able to separate the motherboard from the front side of the calc case, and access the keyboard.
On the 50g, I think all the keys were attached to a plastic framework thing except for the right and left shift things which are by themselves. The keyboard itself looks quite cheap honestly when you take it apart - the posts behind the keys are TINY.
Hope at least some of this is applicable to the 49g+, or someone else down the road looking to fix their 50g.
