It is safe. Laughing gas is safe. It will not cause seizures and it will help with your anxiety during the extraction. Consider meditation , relaxation with a massage prior to your extraction to help with your anxiety. There is a new procedure called nucalm that is great at relaxing you. See if any dentist in your area uses this.
There would be no. Contraindications to the use of n2o as an anesthetic/analgesic adjunct during professional treatment - given your history. Most patients feel euphoric during administration, although some patients begin to feel more apprehensive. Relaying that you have had panic attacks & anxiety to the surgeon/anesthesiologist will be important. Titration is valuable with you, starting low concentration.
Seizures. Yes, safe.