hi
I have done this recently and found you need a day to take out and replace all the parts.. you need new gaskets for the throttle body and the inlet manifold ..you might get away with the rocker cover manifold..The manifolds can be painted with 2 pack paint and a pro lacquer..its better to get spares and paint before you start dismantling
oh yes and spare 10mm sockets for when you lose one down the engine
Check your fuel lines for cracking and remember to fit them the right way up..you have to take off one of the coolant lines to get at one of the manifold nuts The breather tube that goes from the manifold to the block has a spring which has to be compressed before replacing ..use a plastic tie which you cut when in position. Whilst you have the manifold off clean the electrical connector plug ..you might not have another chance
take pics to remind you of what goes where
as to 19lb injectors, I had no probs with the 17.5lb ones but have you done anything else t the car if s they wont make any difference apart from probably overfueling