You might try these.
I have several styles from them.
I had never done this until I bought one.
Took me about 5 minutes maybe to install both front and rear.
I haven't tried any other manufacturers, so I have no comparison.
Their barrel-mounted one is the closest to the Marlin factory sight.
You tap your old rear sight out, tapping from the left to the right, and tap these in.
You will need to file a hair off of the dovetail because they are pretty much
always made just a shade larger to account for differences in the barrel dovetail.
This is true of all dovetail sights.
Their lo-profile is the easiest - it just screws into one of the 4 holes on top of the receiver.
I have one of these also.
With all replacement rear sights, you may or may not need a new front sight.
Again, pretty much true of all choices, from what I read.
I bought the front sight anyway, and just filed it down until it was just right.
Look over on http://www.marlinowners.com/forums/index.php?board=8.0
This is their forum devoted to the 336.
What these guys don't know about the Marlin hasn't been invented yet.
For some reason, the site is down right now (0800 Sunday), but it'll be up soon.