Fix a .NET 2.0 project so it runs on Linux

We have a project that builds and runs fine on windows, we would like it to install and run on Linux under wine (or even better Mono), we are most interested in Ubuntu 12.04 and possibly OSx . The software has run for me in the past to a certain degree with some minor error with auto detecting of drives. At the moment it is not running as it shows a "require Mono 2.0 for Windows error" No doubt this is a solvable problem but I will still be left with the project not working correctly. I need someone to fix the build and give me clear instructions how to install so we can give this to any customers who do not have Windows. For example ideally a Playon Linux script. We do not want to re-write the application entirely as then we will have two projects to maintain and every modification to the windows program will require a corresponding change on the Linux application so it needs to remain in C#