Recently had engineered hardwood installed. It looks bad, marks on boards are inconsistent with samples. Manufacturer/Installer have agreed to provide more material and replace questionable boards. There are 53 boards to be replaced over 1400 sq/ft. Installer states that replacing boards is no problem. It is engineered hardwood glued to concrete . Does anyone have experience with this? Will this look like original installed pieces or will there likely by problems? I don't want to agree to something that may be a temporary solution.

Should not be a problem for a good mechanic. Use the same glue. Cut the bottom of the groove off and shoe-horn them in after cutting to length. There will be a square end on the cut-off, but with a sharp block plane another bevel can be replicated. Touch-up with original finish or a substitute. Weigh the board down if necessary. I use 5 gallon buckets that I get from the commercial painter, who throws them in the trash. They only will need to be weighted for 20 minutes or so, being able to re-use them.