The Canadian Aviation Regulations list the requirements for certifying aeronautical products including repairs. The regulations define a minimum expectation of technical capability to apply for a repair design approval. Repairing a product back into compliance with type design of the product can be complex or simple, so the scope of work will depend on the complexity of the design change.
If you don’t have the required technical abilities, you should source that work to support your application. One place to look is a Transport Canada delegated Design Approval Organization (DAO) or a Design Approval Representative (DAR).
These people and organizations have various technical capabilities and can also act on behalf of Transport Canada to support you in the certification process, including issuing certain types of approvals.