I've taken overnight rides from 3rd to 1st class, quite an experience and definitely one of the slowest way to commute these days. You guys can go there for supper as well & it's usually packed
We actually did something similar - but started from KL to Gemas. Gemas is one of the older stations with a "crossing" (ie they split trains heading east-west in the old days at this station). So u can see many "train skeletons" and a "rotating table" to switch trains around (sorry I don't know the correct terms for these things).