I have communicated with the Archives for years and have never had an issue. Currently, the cost for a document and then the translation into English is 72LT. Use a currency converter and send a check. It's really very painless.
Also, make sure they have your email for future correspondence. In the event there is a correction on a document or a need to send others, they will scan and send via email.
My experience dealing with the Archives has been painless however, at times, has had a delay due to volume.