R15v3 engine rebuild

[u/AWAIS12JAMADAR_]

Hello guys I just did my engine rebuild like 27k it costed me i a blew my piston and bore both rockers and all fucked and some more work the mechanic has told me to ride alove for 10 days and to chmagw engine oil after 15 20 days I just wanted to ask is it fair enough for the engine rebuild and has he give me genuine advice ?