Applicant needing credit fixed

I actually only have one thing on my credit
which affects my credit badly.My ex-husband
purchased in about 1990 or 1991 a Ford Mustang
which i at the time had no credit at all so
in fact my credit was perfect. He purchased and
got approved with Nuvell Financial. I had to
co-sign which was the mistake i've done ever
in my whole life. Anyway when we separted he
gave the car to this older and mature lady
who agreed to keep paying the car.There was an
affidavid that was made which she sign which i
have is in my possesion which states that she was
going to pay the car.But she never did the car
was taken away from her and was sold once
again by the bank. Because i co- signed it
went into my credit affecting what never really
belonged to me.I talked to Nuvell Financial
myself trying to consolidate with them and i
was told that they would settle it at 3 thousand
i asked them for a payment plan. But they
clarified that it was impossible due to the
fact they could only help me by settleing it
with 3 payment in a manner of 3 months. I can
not have it that way though because i don't
have the money. But it something that i do
really want to resolve because i has been
terrible being rejected for any little thing
even for a walmart card.And what frustrates me
is that it not even my fault because i was
separted from my husband and still am and he
was one that made the decision of giving the
car to someone who never paid and had the
pleasure of enjoying the car for awhile.
While my credit is now standing as poor credit
and i know this because i have my credit report
I just don't know what to do i love to have it
corrected and put just on his credit and on his
name since he the irresponisble one NOT ME.
But since i know i am asking for to much i
just want to settle it not lower the same but
with a payment plan. Thank you any help or
orientation will be great.