K.F.
It doesn't necessarily have to cost you more to get them done but you will be responsible for paying a penalty for filing them late. I would probably mail both tax returns in together the 2009 and the 2010. The IRS may consider applying your 2010 refund if any to the balance due on the 2009 return to cover the amount you owe plus any penalty and interest assessed. If you and you husband were still living under the same roof last year, I hope he was filed as Married Filing Separate filing status instead of anything else. Mailing the tax returns in together may get you flagged for an audit and who needs that head ache?
Just suck it up and file it and try to work out payment arrangements but be certain you keep up your payments. The IRS is kinder and gentler but it still has claws and teeth.