Hi, I've just done this a few weeks ago on a 147 I picked up cheaply for my girlfriend. As Ned says the injectors can get stuck, one of mine was but a soak in plus gas and a bit of gentle wiggling and it came out, it looks like the seal had been leaking allowing carbon to build up around it but apart from that it was a nice job to do, 6 of the rockers were snapped and 2 were bent but you should change all 16.
A guy on ebay was selling the rockers for £80 for a set, injector seals £5, belt and pump £120, cam carrier gasket £15.
Whilst it was all apart and as the swirl valves were leaking I also put a manifold on it plus an oil and filter change.
It took most of a Sunday to do but some of that was to change the manifold and now its running great, I just now need to do the wishbones..