Milford Track for Beginners?

Hi

We (couple in our 20s) are thinking of hiking Milford Track in mid April.
The trouble is, the 2 of us have no hiking experience.
I am reasonably fit (eg. can run 5km in 30 mins) while my partner can prob
do it in a little more time.
Hope to hear advice on the following 2 questions:

1) Can 2 non-experienced hikers survive comfortably on the track? Seems from
Lonely Planet and net research that you do not need any experience.

2) Do we need special physical conditioning for the hike? ie. Can a couple
with normal fitness level (ie. run 5km in 30-50 mins) do the hike?

Really want to do the hike, but am not confident at all, esp when I have no
experience and am not sure if I can take care of my partner if the going
gets too rough...

Hope you can help.
Thanks!