Want to buy a Spanish moped. Any advice on tax, insurance etc

Hi have you thought of asking the garage where you can buy it from ? They should be able to give you good advice

My Spanish is not good enough for that unfortunately. 

Take a translator with you?

Have you asked if they speak English? You can always use Google  Translate on your phone and asking can be  fun and a good experience 🙂 give it a go you may be surprised at the outcome