There are set-up help screens to get you through any bits you're not sure of. Once you re online you will have access to the UKF User Zone which contains an email control panel from which you can add news aliases, POP3s and hostnames. Yes, you can. Installing the UK Fantastic software and settings should not disrupt your PC, and leave you with the option of returning to your original service provider whenever you want. Almost nothing, they are virtually identical.
Most computers come with all the required software already installed.
Chances are, you can get online straight away with what you've already got. If not, you'll need a browser to view web pages. Either will do the job just fine and are very similar in appearance. There are more options for reading and sending e-mail. Both Communicator and Explorer come packaged with their own email software, and you'd be hard-pushed to better these for general use.