Do not pay. Unless you teceived a citation or receive a Criminal Summons the incident you refer to will not show on your "record". This is on the civil side, and nothing will show on any search of records unless they successfully sue you for civil damages; they will not sue you. The money they are seeking has NOTHING to do will whether you will get charged criminally. Ignore their letters; they will stop sending them after a few months. Do not talk with the law firm if they use a telephone number you provided at the time. It's a money-making scam for the "lawyers" and the store..
Not necessarily. If you have been fingerprinted there will be a nationwide record. At a minimum there may be a paper trail. You should retain an attorney to make sure you are fully protected and that the best result is achieved.
Your question doesn't say who told you that. I would be leery of anything any store security personnel says. If you receive a letter from a Magisterial District Judge's office that contains a citation you've been charged with retail theft. You will have to be fingerprinted as part of the process. Records of the matter will be available on the internet and as part of a formal criminal history. If you receive a letter from a law firm that is a civil demand latter that does not enter into any formal criminal record and does not go on the internet. If you receive either one, or both, you should speak to a criminal defense lawyer immediately. Good luck.
Please do not do this. Many stores are using this "tactic" against alleged shoplifters. Unfortunately, nothing stops the store from pursuing criminal charges against a person even if he or she pays the $150.00. Say nothing to the store or police about the incident. You should only speak with an attorney about the allegations. Whether or not you already have a criminal record, an attorney should thoroughly review the situation to determine how to best rectify the matter in your favor.