did mine too. launched the boat one afternoon, pulled the trailer into a shady spot, and changed them out in about an hour, then went fishing.
like BSHAW27 said, get all the stuff and prepare ahead of time.
I been guilty of this and seen several others doing it the same way this year. Must be the year of the bunk boards. Now is a good time with boat ramps not so busy and cool weather.
Measure and cut boards, apply carpet, grab cordless tools and some wrenches, load up and go get er done.