Upgrade Macbook Pro from 10.6.8 to 10.8
This is a somewhat subjective question. I would personally recommend upgrading to 8 GB of memory and an SSD, but since you're still within the boundaries of the minimum specs, there's no definitive answer. Outside of making sure that all the software you'll need to have working will work, you don't really need to consider anything. I would personally recommend upgrading to Mavericks as it's better supported and optimized then Mountain Lion, and El Cap is not out of the question either.