re: Concrete Help

I'd rent a gas powered concrete saw before I rented a jackhammer. You could also use a jackhammer to breakup channel you cut out. I'd just give it couple licks with a sledge hammer though.

When cutting channel in sidewalk be sure and cut straight parallel lines so the repair looks neat as possible.

Make sure you exhaust your options on digging under the sidewalk first. It might be a PITA but renting a saw, cutting concrete and repairing isn't an easy time either. Not to mention you'll probably always be able to tell there is a patch in the walk.