I have a shoplifting ticket from Walmart, classified as class 3 misdemeanor first offense, can i represent myself and plea-bargain for littering?

I doubt there will be an agreement to drop it to "littering" - in my experience that would be unusual. It depends a lot on the Court you are in, but it may be possible to negotiate a "deferred sentence" which is where a person pleads guilty but the sentence is deferred. Conditions are attached to the probation on the deferred sentence - like a "petty theft class", community service, etc. If those are successfully completed in the time required, then the guilty plea gets withdrawn, and the charge is dismissed, leaving no conviction at all. It is then possible to "seal" the record by filing additional paperwork at the end, which removes the case from the public record and you do not have to disclose it on future application for apartments, jobs, etc.