Personally I like the inground method. Yes more involved but a much better installation. Get a water jet digger(not sure if thats the right name) to get under your walkway. You should be able to find one that screws onto a 1"or 3/4" male pvc adapter. That will minimize the digging in that area, for the rest get a small trencher from the rental store. Just make sure your lawn is damp before you trench or it can be a real pita. Also plan for a way to purge the new line before winter hits or youll dig it up every year.