How test this code with Moq and AutoMapper

Question

I have no experience on writting Unit Tests and I am starting with it. My project has a Data Access Layer (with nhibernate) where I have repositories that are injected by an IoC container into some Services in a Business Layer. I want to write Unit Tests to test some methods on the Services (business Layer). I know it is important to have Moqs to simulate the Repositories and avoid hits over the dataBase. I would like to know how to test this method:

public bool AddNewProject(ProjectViewModel viewModel)
{
    // _projectRepository is an interface: IProjectRepository, resolved by IoC container
    if (_projectRepository.ExistsNumber(viewModel.Number))
    {
       Validation.AddError("Number", GlobalResource.DuplicatedNumber);
       return false;
    }

    if (_projectRepository.GetTotalAvailable(viewModel.ItemId) > 0)
    {
       Validation.AddError("ItemId", GlobalResource.NotItemAvailable);
       return false;
    }

    var project = Mapper.Map<Project>(viewModel);

    project.Data = _projectRepository.GetData(viewModel.ItemId);

    _projectRepository.Save(project);

    viewModel.Id = project.Id;

    return true;
}

I know I have to write at least three unit tests, one for each validation and one for success. The problem is that in the AutoMapper configuration, I have my IoC container resolving a type the AfterMap event, for sample:

config.CreateMap<ProjectViewModel, Project>()
      .AfterMap((vm, p) => { 
           // it is necessary because nhibernate will save this relation
           var cityRepository = container.Resolve<ICityRepository>(); 
           p.City = cityRepository.Load(vm.CityId);              
       });

I saw in some place on the web that it is not necessary to have the IoC container in the unit test and I should Moq just the methods I need (not sure if it is correct). Should I have to define memory repositories and register them on a ioc container on the test project? I would be difficult to test because i need to rewrite all the repositories (more than 300).

Obs: It is difficult to change because there are more than 300 entities using Repository.Load to make associations on the AfterMap event on the AutoMapper.

This is my unit test:

[TestMethod]
public void Should_not_save_a_project_by_existent_number()
{
    var viewModel  = new ProjectViewModel();
    viewModel.Code = "PJT";
    viewModel.CityId = 1;
    viewModel.ItemId = 1;
    viewModel.Name = "This is a test";

    // for the validation, I use this simulator in memory (in asp.net mvc I encapsulate the ModelState)
    var validator = new MemoryValidation();
    var projectMoqRepository = new Mock<IProjectRepository>();
    // I will mock methods here...

    var projectService = new ProjectService(projectMoqRepository.Object, validator);

    // the ICityRepository is defined on the IoC, so when I call AddNewProject
    // it will be resolved inside the AutoMapper context on the AfterMap event.
    // it is not injected on the ProjectService ctor.
    var result = projectService.AddNewProject(viewModel);

    projectService.Validation["Number"].ShouldNotBeEmpty();
    result.ShouldBeFalse(); 
}