Can I change widget design of e-Newsletter plugin?

If I can do,I want to change the widget design of e-Newsletter plugin.

...

Now,I use e-Newsletter-plugin's short code [enewsletter_subscribe].

I use my own css to overwrite native your design.

But I really want to change the HTML code of [enewsletter_subscribe].

Can I do that?

(I know, if I change your native php code of e-Newsletter-plugin,It is really danger.
Because,When you update your plugin,My changes will be overwritten..)

Regards,
Koji