i got a loan from my 401k for my wifes surgery.after repaying on the loan for 4 months it went into default because i was laid off my job.now im hit with a extra 10% penalty besides the 20% tax i have to pay on it.i claimed all the medical expenes on my tax returns last year. i had to get an extention for this year so i could figure this problem out.my question is:do i need an expert cpa on 401k distributions that can revise my previous taxes to include the taxes and penalty sense i claimed the medical and my taxable income was much less last year?

You CANNOT carry back the 401K distribution, because the initial distribution was a LOAN, not a taxable distribution.

Correct, when you got laid off you had the chance to pay off the loan and then roll over the distribution. By not doing so, you incurred a taxable event in the year you defaulted and got a 1099 for that year.