The coordinates will take you to a plaque dedicating the Rum River Trail to Henry Hammer.
On the plaque is a date. To find the final stage subtract the first 2 digits of the 4 digit year from the latitude.
Then add the first and fourth digits of the 4 digit year together and add them to the longitude. This will take you to the final stage.
You can validate your puzzle solution with
certitude.
Jvgu lbhe onpx gb gur evire gur pnpur vf nybat gur yrsg fvqr, abg vafvqr.
Abg jvagre-sevraqyl.