I put my Marlin in the Muzzelite bullpup stock about 15 years ago. I love it, but it's a double edged sword. It balances great and points instinctively. The downside is the trigger setup adds some mush and extra weight to the Carbine's already overly heavy trigger. Since it's only a 9mm and isn't a long range cartridge, the bullpup works out very well for the gun though.
The sights that come on the stock kit are adjustable but a little coarse. That's fine on a pistol caliber plinker though. The gun really came into it's own when I put a red dot sight on it. You can easily nail man sized targets at 100 yards with 100% reliability, but the heavier trigger does tend to affect your groups.
It's a lot of work to disassemble (and rezero) for thorough cleaning, but if your Marlin is like mine, it'll run practically forever with nothing more than a little oil applied to the moving parts. I pull mine apart every few years to detail clean. The rest of the time it gets an Otis pulled through the bore and some oil applied to the bolt.
I like the bullpup stocks enough that I added them to my gun show sales and have gotten a lot of positive comments from folks who have bought them.