Tax reporting on 2001 tax letter on installment sale main home repossession?

taxpayer didn't file taxes for all back years. He has a bill from 2001 1099S that he says are an installment sale main residence sale bought in 1984 sold in 1987 and then was defaulted on in 2001. Main home exclusion was taken when it was sold. Now how is it reported? Does it retain any of the exclusion character or is it now considered income. If so, how would he figure out the basis? Thanks!