I would suggest you put it in both places as you cannot guarantee the employer will have the correct software to view the attachment. Just make sure the email is done neatly and professionally and is free from unusual fonts, colors, or other formats. I would suggest you also mail a hard copy to their current address. Source: personal experience

In theory, I'd have the resume in the text of the email. So it is guaranteed that the employer can read it. There've been too many cases of "cannot open attachment" in my experience also! Of course, a resume in the text of an email may not have the nice layout of a proper document. So if I do an attachment, I use pdf format. I believe most modern wordprocessors are able to export or save a file as pdf - I use OpenOffice.

industry standard is usually to attach a Word document to the email.