I have experience with these cases over 17 years.
This is a case that usually starts as a misdemeanor, and now, turns into an infraction in many cases.
As a misdemeanor, you have a right to a public defender and a jury trial. They may reduce it for you before your first court date. If not, show up on time, ask for a public defender and go from there.
A public defender will know exactly what to do.
If you do not have any other petty theft convictions, your penalties probably will not be enhanced.
Dont worry about misdemeanor trespassing convictions from the past. They are not relevant to your current citation and will not cause a problem. Theft convictions will cause a problem.
This is a case that is also commonly referred to "diversion", which means "deferred judgement" and often results in dismissal when certain classes and conditions are met.
Show up for your court date on time and ask for the public defender if you cannot hire a private attorney early.