Is the ribbon cable attaching the keyboard to the computer damaged or loose? Is there any crud under those keys blocking them from moving up and down normally? You can GENTLY try to dislodge any detritus by GENTLY tapping on the back of the keyboard; the key word here is GENTLY, because you don't want to cause MORE damage, or knock any keys off. Those keys are close together, which makes me suspect some cookie crumbs or corn flakes are preventing them from working properly.
Check the keyboard for the problems I mentioned; chances are, you can fix this fairly easily. If not, try to find someone else you can swap keyboards with; it is entirely possible that your keyboard is damaged beyond repair, so you might have to replace it.
First choice is to look for problems blocking the key travel; don't spend a dime on a new board until you're SURE that yours is defective.