I would avoid the main dealer unless you really want to keep a main dealer FSH
There are a few good Subaru Specialists on here who will do the job at a fraction of the cost
Closest to you would be Darren at DLM in Darlington - he doesn't advertise on here but is a well known Subaru mechanic: 18 Percy Road, DL3 0RX Tel: 01325 480678
Next is Chester Le Street and you have Andy Kindon & Drew Bailey - both are advertised in the your business section on here:
SUBARU SERVICING etc etcDrews Autos - 6 Conyers Rd, Chester Le Street, county durham, DH2 2HD Tel: 07843 421838