The largest part of the conversion was lifting out the 36 tonne cricket pitch and replacing it with the same weight of turf, using a 16-tonne machine.
Up to 150 people would be needed to mark the pitch, clean the stadium, change sponsor signs and haul out retractable seating in front of the south stand.
"The worst thing that could happen would be for it to rain," he said.
"It's bad enough visibility under the egress lights. Everything is in heavy shadows already."
The opening round of the NRL was expected to be the highest attended in the history of the competition as Eden Park pulled the largest crowd of 38,000.
The next highest anticipated crowd was 29,000 at Hunter Stadium for the Newcastle versus St George game on Thursday night.