I have a debt in collections. If I pay it, will it be removed from my credit report?

No, unfortunately you won’t notice an increase in your credit score immediately after paying your debts to collections, as it will still be on your actual credit report. However, you can write a letter of appeal to the creditor/collection agency after paying off your debt, requesting that they expedite the removal of the associated negative information from your credit report. After that, you will hopefully see an increase in your credit score.

Yes and no. Just paying the debt won't clear the collection, it'll just be updated to show 0 balance. While it's obviously better for you to pay it off, your score won't change for it. 

With that said, many collection agencies accept a "pay-for-delete". That just means that, if you pay off the whole sum, they'll agree to delete the listing from your report. Of course, not all of them go for it, and you have to request it, but it's worth a shot.