Website re-design

Our website currently has all of the functions we need it to have - the problem is that it is quite ugly and has a poor user interface (due to the way it looks and feels). It is similar to a procurement portal - and includes functions such as subscribe, auto email, filtering and other similar functions.

We'd like someone to change the look and feel of the website without messing up the functionality of the site.

what would be ideal is if we could contract someone to complete the work in stages . This will help us to make sure we are getting what we asked for and also help us stagger the progress to make sure we are able to do a good job.