Hi ross14,
It's not clear what you mean when you ask how "important" these two Quant categories are. They're two of the rarer Quant subjects that you'll face in that section - while you'll likely see 1 of each on Test Day, you likely wouldn't see more than 2-3 of each in total. While some Combination and Permutation questions can be quite difficult, many of them are actually pretty straight-forward prompts, once you know how to properly approach them. If you're "far" from your score goal in the Quant section, then these question types aren't worth your time - the 'bigger' categories offer far more questions, and are worth far more points overall, than either of these two.
1) How have you been scoring on your practice CATs (including the Quant and Verbal Scaled Scores)?
2) What is your score goal?
GMAT assassins aren't born, they're made,
Rich