96 aspire egr problems

I just spent $500 replacing the plugs, cap, rotor, EGR valve, and EGR solenoid on my 96 Aspire and the check engine light came back on after the car had been on the road again less than 25 miles from the shop. I was assured by the mechanic ( note mechanic, not technician) that his shop would be able to correctly diagnose the check engine light's source. On the invoice the mechanic wrote "May need additional cleaning in the EGR ports". When he talked about this he said it was a labor intensive job that would be

3 to 4 hour labor time. Before I throw in another 400 bucks in this vehicle should I perhaps take it to the Ford garage to have them analyze the cause of the check engine light? Thanks in advance