If you know how to uninstall and reinstall the new lock again, then you just need a replacement mortise lock body. If you can find a brand name on it and get an exact replacement, then you can reuse your gripset and remaining hardware.
Different brands have different measurements so its not as simple as just getting a new mortise lock.
Also is this a condo? Dont know how it works in HK, but here in Canada, even if you own the condo, if the integrity and/or security of the lockset is compromised in anyway and it wasnt your fault, building management usually has to cover the cost. Fire laws and all that. Just trying to cover as many bases as i can think of for ya.
TLDR: If you know exactly what youre doing, you can replace it assuming you know where to get the replacement. If not, call a locksmith.