I recently conducted some tests. It depends on how many and what types of tests you are translating, and you have not killed yourself by giving us details. In general, I think it is safe to assume that your average MSTest store will not be massively infected and thus will not be immersed in every dark corner of MSTest.
All Assert.* Methods and basic test attributes are easy to find and replace. The more rare, I tend to direct myself to evaluate each case individually. If you are no longer an expert at xUnit.net, you have many opportunities to learn, and this will help you.
In addition, using Assert.Fail not a simple conversion. Converting TestClassInitialize to IUseFixture is another thing, but simple but difficult to automate.
If people use test links, you won’t be able to remove the link to the MSTest assembly (and you will still need to have VS on your build server), and it will continue to randomly fail on Shadow taks, see my questions).
The biggest manual work for me went through 20 lines of the template in the area at the top to see if anyone really used any user attributes before deleting them.
The main thing is that there would be a lot of work if it were not for the CodeRush template that converts ExpectedException to Assert.Throws . If you did not receive CodeRush or ReSharper on this assignment, you would steal money from your employer.