Don't damage gutters by propping a regular extension ladder against them. An articulating ladder bends to go up and over the gutter, transferring weight to the roof (Image 1). Many home improvement stores rent articulating ladders.
If an articulating ladder is not available, prop an extension ladder against the side of the roof (Image 2).
Begin by cleaning debris from gutters. Use a scoop and a bucket to avoid leaving a trail of debris around the house (Image 3).
Position the 2' x 4' section in the gutter to brace against the force of the hammer, and pry out old gutter spikes one at a time (Image 1).
Install a new threaded spike using a drill (Image 2). Repeat the process until all of the spikes have been replaced one by one.
Now snap the gutter covers into place. Most vinyl covers have a flat edge that slides up under the shingles and a channel on the other side that snaps onto the lip of the gutter.
Make sure you put in downspout protectors before installing the covers.