Remove the old planks from the wood porch with a pry bar and claw hammer. Start on one side and work to the other side. Remove one plank at a time and place it on the ground in the same manner they were arranged when fastened to the porch.
Pull any nails protruding from the exposed porch joists with a claw hammer.
Measure each plank, one at a time, using a tape measure. Then cut new planks to the same lengths with a circular saw. Wear eye protection and a dust mask when cutting new lumber planks to fit.
Fasten the new planks into place, one by one, going from one side of the porch to the other by driving stainless steel nails through the new planks into the deck joists.
Attach medium-grit sandpaper to an orbital sander and sand the new porch planks, removing any splinters and smoothing them. Then, sweep off the porch with a broom once sanded smooth.
Apply at least two coats of wood sealer with a paintbrush, waiting at least three hours between coats or as long as directed by the manufacturer to finish replacing your wooden front porch.