If you have a split plea and a straight (reported) conviction to any charge - in this case the theft charge, you are not eligible to have the case sealed. You can not only seal a portion of the case - the deferred to the burglary offense. Either the entire case can be sealed or the entire case can not be sealed. In your case, the entire case simply can not be sealed. So, although I am sure that your public defender and probation officer had the best of intentions, they provided you with statement that run contrary to Colorado's statute regarding the sealing of criminal records. Your case can not be sealed. With respect to possessing and owning a firearm, in all likelihood you will not be able to own or possess a firearm during the course of your deferred or probation. However, once the deferred is dismissed, you will not have a felony conviction and the misdemeanor offense is not a domestic violence that would prohibit your possession of a firearm under federal law. As such, given the facts that you have presented, I do not see anything that stands out that would prevent you from owning a firearm in the future. However, it is always best to double-check with an attorney after you complete your probation and deferred judgment and sentence to make sure, in order to avoid getting in further trouble.
Ordinarily a felony conviction will bar you from firearms ownership. Don't take a chance on being charged with being a felon in possession. Federal enforcement of that charge is fierce, and carries a mandatory minimum five years. Federal sentences are real time, no time off for good behavior like Colorado.
This answer does not create an attorney-client relationship. It is advisable to consult with an attorney with full disclosure of relevant facts for a comprehensive leagl opinion.
A felony conviction bars you for life from possessing firearms or ammo. It depends on the law of the state where your case was handled (Colorado I presume) whether your case resulted in a felony conviction or not. I will defer to Mr. Leroi on that one, and he appears to have provided you a good answer. You may want to think about hiring him to figure this out for you.
Additionally, even if you do have a felony conviction, federal law allows for you to regain your firearm rights by "expunging" or setting aside your conviction. Again, whether you can do this depends on Colorado law, and I practice in California, so I will again defer to Mr. Leroi to determine whether this is a feasible option for you.
Until you figure this out, you would be wise to avoid ALL firearms and ammo. That means no hunting, no range, nothing. I have multiple clients who get charged with felonies for having a few loose cartridges around their house, even though no firearm is present. Law enforcement is very serious about these charges, easy pickings to re-jam up a felon.
Michel & Associates, PC
All my comments here are intended for general legal purposes. None of my comments here establish an attorney-client relationship with anyone. None of my comments should be relied on in taking legal action without first consulting an attorney.