CHOCK YOUR WHEELS OR USE THE E BRAKE. Remove your driveshaft, use some type of penetrating oil and remove the large nut and washer holding the yoke. You can use a puller if you have one or just use a hammer to break it loose. Mark the shaft and yoke to reinstall it in the same place it was removed from, pry the seal off, clean and gently tap the new seal into place. Reinstall the yoke and driveshaft and you're done.