How can I change the Subscriber Email to be left justified and truncate after some text (readmore)?

Hello,

I'm needing to change the email that goes out to blog subscribers so that it's left justified (not centered) and has a "Readmore".

If we add a "readmore" to the blog post will it reflect this in the subscriber email?

I see from other posts that there are two files to edit - both PHP files (email.blog.new.html.php and email.template.html.php) and I don't know PHP. I'm hoping this is clear once I get in there.

That said, if I change these files, will they be overridden after every time I have to update EB?

Any assistance is most appreciated.
Thanks,
Jenn