I have a new inner chainring to fit on my compact,is this do-able for a novice like me? Any special tools needed? The BB is a Shimano hollowtech II i think,it's not obvious to me where to start apart from removing the outer chainring first. The new ring is slightly bigger so i'm assuming the gears will need setting up afterwards. I can get the mobile mechanic to come round but you know,if i can save a few quid.......