i would use a genuine kit on the timing and balance shafts,the pattern kits are nowhere as good as the genuine kit plus vauxhall/opel have updated the kits over the years,no you do not have to remove the engine but you have to lower or raise the engine to get some of the bolts out,the job i believe on a vectra b is about 4 hours as it is a slightly harder job to do than on the astra