You could try alittle warmth on the linkage, don't use a blow torch, you'll wreck the gaerbox seal, get some very hot water and soak a towel in it, put on some gloves and wrap it round the linkage, this might warm it up enough to loosen the pin. You may have to use the towel a few times though.
Don't really want you paying loads for Vauxhall to do it............
Put some wd40 or plusgas on it before applying the towel...
Oh yeah, don't tell the missus what yoou need the towel for !!!!!!!!!!!!!