Unfortunately, the dollar amount puts you in grand theft range. Grand theft is a "wobbler" and can be filed as either a felony or a misdemeanor. As a felony, anything from probation and no jail time to 3 years state prison are possible. As a misdemeanor, it carries up to a year in county jail.
Will you get jail time? That really depends on the details of the case, whether restitution is paid back, the merchandise recoverable, etc. - and most importantly what your attorney can work out for you.
You absolutely need a criminal defense attorney. You've got less than a week, but it's still time to set up meetings with a few and retain the one you're most comfortable with.
When you appear in court, ask the judge to appoint you an attorney. As you were obviously terminated, I doubt that you have the funds to retain an attorney. You need not say anything other than your name and ask for an attorney.
Also, definitely appear. If you do not, the judge is likely to keep you in custody when you are brought in on a warrant.