Altering a JetPack module without modifying it?

Hi, I’m not sure this can be done. But I am setting up some forms in one of my sites using the JetPack plug-in. I thought it might be simpler and maintained as I’ve found my previous solutions breaking from time to time.

Anyway, I have themed as much of the form as I can but there are things I can’t alter to match other parts of my site. Thinks like putting PLACEHOLDER into the INPUT tags, change the (required) to something less intrusive and familiar such as *, and finally. I have a nice little button I like and would like to replace the awful looking SUBMIT>> link.

Basically I want to make this:
http://www.burragallery.com/gallery-emails/email-brook-gerard
Look like this:
http://www.burragallery.com/search

NOTE: That email is to me.

I’ve never used a child theme. But can I use this to alter the plug-ins template?

Cheers,. Brook