Sounds serious bud. Might be worth taking it apart again like krzys says, although not a lot you can do with gearboxes if you're not a specialist. You'll find a d series gearbox in most breakers yards mate, very easy to come by. Phone some local breakers and ask if they have any 1.4, 1.5 or 1.6 civics in. Even one from a 3 door should fit I think.