No, the bubbles will not harm your fish or the corals. They are simply unsightly and increase saltcreep.
I would let him work on it, you may as him if he can just build a bubble trap.
Personally I prefer a sump over a canister on a SW
you need a skimmer. The skimmer removes proteins and other junk directly from the water column. You can get around having one, but it requires daily water changes, which is just as expensive in the long run.