First, pay off any current debt you might have... anything you make payments on, anything not in collections.. once that is done, and you have a small savings fund for emergencies, then do teh old debt..
First, call the lender, not the collector, and see if they will settle with you (if they didn't sell the debt to a collector yet, they will likely settle with you for less than you owe.) Get it in writing from them what the "deal" is - i.e. youwill pay $1400 to them and theywill set your account status to "paid in full, nothing owed" for the $3000 you do owe them.
If your debt was sold to a collection agency, then I'd suggest paying them with a money order/cashiers check (since it's not linked to your personal $ in any way) and NOT use a cc to pay off another debt. Yes, some shady collections folks (and some not so shady ones) will take your checking acct. number adn then withdraw whatever they want.
Mkae sure you get it in writing from them that you have paid. Make copies of the check and letter when you send it in, store it together, etc. so you have proof for the credit agencies later on.
Never give them access to a cc (they can submit multiple charges) or your checking acct or debit card #.
Good luck!