I would say a couple hundred dollars for your average shop. its maybe a 2-3 hour job for them, just look at thier hourly rate, or call around, most shops can give you a good estimate on a simple job like that.
I would personally advise doing it yourself. if you have basic hand tools, and a spare saturday, you can have it done yourself. especially since its stock PI cams, you dont even need to take the front cover off to time them, just throw them in straight up on the factory timing marks.
pop intake off, all the associated stuff on top of the motor, take the valve covers off, unbolt the cams. swap cam gears, spacer and bolt w/ washer over to new cams, put em in, torque them down. install followers, then valve covers, them intake and all your top end stuff.
turn that bad boy over, and enjoy. even for a first-timer, it shouldn't take all day, even if your going by a manual or a step-by-step write up.