Joey – before your post drops off the bottom of the list, I’ll offer this response.
Depending upon any By-Laws of your Plan to the contrary, the maintenance, repair, and replacement of exhaust fans that are connected to a common ducting system is the responsibility of the Owners Corporation (O/C), and any that are “stand alone” such as yours is the responsibility of the individual Lot Owners concerned.
Although the Owners’ Manual of your Plan doesn’t state who’s responsible, that is why it differentiates between the two (2) types of installations; the exhaust fan in your Lot is your responsibility.
As a side note, it’s likely that your O/C was prepared to obtain a quotation for and to oversee the replacement of your Lot’s exhaust fan because there’s almost certainly a duct between the fan and the outlet grille that’s fitted to the face of the external wall, and if that’s not properly connected with the new fan unit then the moisture-laden air from your bathroom will rise up the wall cavity, and very likely cause damage to the Common Property for which the O/C would be responsible.