Sir i dont think you can actually replace the Water Body (water pump) seal. You need to buy a new water pump. Not a high cost though.
Also after the overhaul, please try to use a good quality coolant as it saves the internals from rust for quite a long time and saves you the occasional radiator cleaning and water body replacements.
Also i would second Mr. Xulfiqar about the hydraulic lifters. A good mechanic always keeps tracks of the lifters (which came out of where). Ask him to do a thorough service, by opening the inside cylinders, flush them up with petrol, clean them "ONE By ONE". I repeat "One by One" to keep track of what parts belong to which lifter. Then soak them in engine oil, re-assemble them. And test by plunging them by hands to observe a resistance free motion. For these are the lifters that get un-plungable due to late oil changes and poor quality oil.