oil pump balance shaft

hi everyone new guy here need input.....97 cavy 2.4 193,000 miles motor still in ..head and everything else off Iam now trying to change oil pump but screwed on this balance shaft deal IS it possible to remove the half section of the shaft housing and change out the oil pump. Motor still in car with out having to keep balance shaft alignment like haynes says the rest of motor already lined up (crankshaft ) sending head out and i dont see the sprocket line up like haynes 2B-13 pic 14.18 shows.....or at what point can I stop on 2B-12 pg sec 14 and get the last bolt out of the oil pump ? Thats enough any input would be great, Thanks

post to self either pull trany pan for better line of sight so that you can use feeler gauge to reset tensioner also find out why I dont see the gear alighment marks ? and I have not got any response here . I guess we will just pull the motor heck whats left after all this a/c drop it, ground wires mark those ,trany wires mark those got floor jack engine lift pull the trans axles ..was going to change the seals any way and have to replace the drivers hub take off last motor mount

at least I can change rear main seal if I go a head and pull motor and yes learn more about this balance shaft deal ...heck why stop there might just order rings and rods bearings too well heck I have all ready replace the exhaust system since it was burning rich and burned the cayletic up and 2- o2 sensors should have left well enough alone. I mean who takes apart a car you just got back in shape any way the car was bought for 300.00 and found the vac hose split down the side you could not see from the TB to map sensor comments - suggestions???

ok so the motor is finally out and the sprockets that haynes shows are in side the balance shaft housing could not see from where I was and the half moon pics were of the motor up side down and to beat all the last bolt to get to the oil pump was accessible through a hole just in behind the balance chain. Damn what a lesson Im gettin ...well any way the pistions are out no instruction on how to do the cylinders (take to machine shop)think Ill just get some new rings and throw it all back to gether