1999 Other Fiat Models power steering problems

Steering problem
1999 Other Fiat Models V8 Wheel Drive Type unknown Manual 64000 miles

Hi
Wondered if you could help me please, I have a fiat punto elx 1999 1.2 the power steering has gone, the power steering light is permanently on, it worked for a week then went off and was intermitten for a week or so, now it has completely gone, It has now failed its MOT, I have taken to a garage yesterday who said he was 95% sure it was not the column but the pump but to go to a fiat dealer and get them to check it out, I took it today but they want £90 plus vat to do a diagnostic test on it, I thought this a bit steep, was wondering if you could help, I was going to get a 2nd hand pump and try to see if this worked, I would be very grateful if you could help.
thanks in advance

Lorraine