1. Whether you use a comma or a colon is a matter not of urgency, but of personal taste. You can use either (the colon is becoming more fashionable), but choose one and stick to it.
2. Commas can sometimes be used to mark off parenthetical phrases. If you decide to use parentheses instead, you should definitely not use the commas as well -- that's really too much of a good thing:
The Queen, who was bored to tears, fell asleep.
The Queen (who was bored to tears) fell asleep.
The Queen -- who was bored to tears -- fell asleep.
The "parentheses" version here is more old-fashioned than the other two.
Sometimes you do have parentheses and commas, like this:
Having cooked a meal (which she considered part of her wifely duties), Susan shot her husband.
That's because the comma is still needed even if you remove the parenthetical part:
Having cooked a meal, Susan shot her husband.