I wouldn't ride much with three broken spokes. Three will lead to four, which will lead to five and pretty soon you need a complete new wheel. A dealer can do it. It can be done at home, but it is such a PITA, that I paid a local cycle parts dealer $25 to do it for me (I supplied the spokes off of an extra parts wheel I have). Call a dealer and ask what they would charge and call a local aftermarket cycle parts store that sells tires and ask what they would charge. Either way, you'll save $$ if you take the wheel off the bike and take it to them.