sir @pwuser170272559793 your mechanic is cheater crook without any idea how to overhaul an engine., thus suggesting a swap from junkyard.
as i have understood by reading this forum posts, nobody sensible is so perfect to declare an engine weak & recommend overhaul just by a strange sound.
please goto a workshop which can perform compression test (wet & dry) both psi values for all cylinders are mandatory to ascertain next step to resolve your problem(s).
wagon R is Suzuki PKDM vehicle engine overhaul parts are available in abundance.
please mention your location in next post for further guidance.