More than removing the existing shingles is the manner of decking typically installed for a corrugated roof.
Decking is 1x4s installed alternately up the rafters. Start at the bottom edge and nail down the first row, space a 1x4 width, nail the next row. We normally get the first row in place, stack up a group above it, and nail off the boards in every other row. (Nail all odd rows going up) After you have nailed off a few rows, you remove the alternate boards and move them up as you need more.
Decking is 1x4s installed alternately up the rafters. Start at the bottom edge and nail down the first row, space a 1x4 width, nail the next row. We normally get the first row in place, stack up a group above it, and nail off the boards in every other row. (Nail all odd rows going up) After you have nailed off a few rows, you remove the alternate boards and move them up as you need more.
