Hi. I live in Madrid and I am a fluent English speaker. To be honest, I never sent such a large amount of mail. But I would be happy to go with you to a post office and find out what the process is, and then help you with whatever is required. Regarding my fee, it is hard for me to tell as I'm not sure how much work will be necessary, I would expect something around 7 EUR per hour if that sounds fair. We can discuss once we find out what needs to be done, so I can try to translate that in hours to provide you with a quote.