Decompile and rewrite

We are looking for an experienced developer to make some enhancements to an existing automotive application. This project will require the ability to decompile existing code and make modifications as required. The enhancements are largely security related in nature and we would essentially like to create a limited user view of the menu system and restrict overwriting a few fields. The candidate should ideally have a minimum of 5 years of development experience with the following technologies: Visual Basic, .NET, C++, and MS Access.