The Marlin's have had several different sight set ups available. Most typical is a dovetail mounted rear sight with a step ramp for elevation, with a screwed on base with a dovetail mounted front blade.

If you have this set up, I personally would drift the front sight and keep the step ramp centered on the barrel in the rear sight.

Brute force method: place the barrel in a padded vise, use a brass punch and a mallet to drift the sight in the dovetail (opposite of where you want the bullet strike to move).

Poor man's sight puller: Padded bar clamp with a drilled and tapped hole near the top edge, small bolt mounted in hole. Mount the barrel in the padded clamp with the bolt positioned to push against the sight. Place a piece of cardboard or leather between the sight and the bolt, turn the bolt to press the sight.

Works with a pair of flat grip vise grips also.