WIthout any prior experience with customizing wordpress, I think completing this in 5 days is gonna be a challenge... but you can try.
You need to
1) get a web host with cpanel (if it has fantastico, quick install, and myphpadmin, it would be quicker.)
2) install wordpress website in to your test domain
3) access the ftp client to tweak the wordpress template in wp-content/themes/twenty-eleven/
4) in there, you can tweak the CSS and PHP
- You can install plugins for sideshows, recent post, features, lightbox, and more.
- You can also edit the mainmenu navi in the wordpress dashboard
After you finish tweaking, you take the wordpress files and upload it in to the client's server. You also have to export the mySQL data and import into the client's myphpadmin.
make sure you edit the wp-config.php with your username and password of you won't be able to access the blog other than their web host (which is tough to access because it contains client's personal information..Usually you dont' ask to access client's web host.)
go to wordpress.org for more information. Remember, it's not wordpress.com, it's wordpress.org.