Been in that boat before. It sucks but once you bite the bullet and actually call the IRS and work out a payment plan, it's not that bad. They do charge you a fee, I believe it is like $50, to set up the installment plan. Also you don't have to pay that fee upfront; it gets tacked onto your existing debt.
From there, they do the math based off your income ability to pay back the debt vs the 6 years max to pay it back. And you can either pay the minimum over those years or pay more and get it over with quicker.
They do charge interest, though it's far lower than say a credit card. Don't quote me on this, but it's in the neighborhood of 4-7%. Think it depends on the year. Either way, I would ask that question and anything else you can think of when you call in to set up the installment.
After that, you make payments through an online portal. EFTPS is the most common option, and the one they will recommend. I would recommend registering an account on there as soon as you can (if you know you will be going for a payment plan) as it takes several business days to get your PIN for the site.
Also, if anyone needs help using that site (it's not the most user friendly) let me know here. Happy to help. Can be a little tricky the first time around.