Do you need to replace the front sight? - No.
You can do it a few different ways.
One way,is to remove the barrel rear sight, filling the dovetail slot with a filler blank, and just use the tang sight as you would any other peep.
Another way, would be to zero a folding leaf rear barrel sight for short range (say, 50-75yds), and zero the tang sight for a longer range (say, 125yds). If you hunt the brush with the barrel sight, there'll be enough time to unfold the tang sight, if game is spotted afar.
Anyone use tang sight on a Marlin, which brand? - Yes.
Pay your money & make your choice.
The Lyman is less expensive than the Marble's, but the Marble's has click-adjustable W&E, while the Lyman must be shimmed under one side of the base to adjust windage.
The Marble's has a thin upper stem, while the Lyman appears more robust in that area.
Both are available for the least money, AFAIK, from MidwayUSA.