how difficult is it for first years to obtain a job on campus?

depends on what kinda job you are looking for.... my friend worked for the conference services and made $11/hour, 40hours/job and loved it.
Plus it doesn't hurt to apply to all, good luck =]

It depends on a lot. There are some jobs on campus that are open to all students (like working at Union Market for example). You might be able to get this job if you're in first year, but it depends on your experience. Check the MSU website for these job postings.

There are lots of other jobs, called "McWork" jobs, that are only open to students who show "financial need", in second year and above.