Welcome to the forum!
About wiping Windows XP, Do Not Do It! For this reason and this reason alone: if you also use your laptop for business, you're just going to need some Windows exclusive apps. (Microsoft Office, maybe Photoshop, etc.) So you will want a dual partition (% of Linux, % of Windows). This is incredibly easy to do, when you boot into Linux and begin to install, it will ask you how much of your disk (HDD or SSD) you want dedicated to Linux, it will also let you know how much Windows still needs to be a functioning OS. (Though I would never give your Windows partition anything less than 20% of your disk space, unless your disk has about one Terabyte of space.)
A distro is a unique Linux OS. It is a fully functioning OS just like Windows or Mac OSX. You would just download the distro from the distro holder's website.
Which distro to use depends on your needs, really. If you live in the US, Japan, or other country that requires you to BUY your codecs, then the distro that includes non-free codecs is not an option for you. (Such as some flavors of the Linux Mint distro.) You would then have to BUY your codecs from third party vendors, such as Fluendo (I have done this and they work fine.) Or some other codec purchasing company.
I'll give you links to the two most popular Linux distros, and you can judge for yourself.
About: The most popular Linux OS on the planet, you can only use the Unity interface if you use Ubuntu (you can get Xubuntu or Lubuntu, or even, Kubuntu, more on that in my second post here), very comfortable to use. Uses .deb packages.
About: The runner up for popularity in the Linux world. You can pick from four interfaces: GNOME, KDE, LXDE, and Xfce. Uses .RPM packages. The DVD version has a MIND BLOWING amount of apps included, dwarfing Ubuntu's STARTING base of apps. (You can always download tons of apps for Ubuntu from the Ubuntu Software Center). I find Fedora isn't nearly as user friendly as Ubuntu, but it's not bad at all for those who know what they're doing.
Hope this helps, and again, welcome to the forum,