If you are still using a computer with XP be sure your antivirus is up to date and stop using Internet Explorer immediately. Instead, use Firefox or Chrome to browse the Internet and make sure whichever one you are using is up to date.
Your computer will continue to function normally and most likely you will not experience any issues now that support has ended. Over time however problems will arise with compatibility and stability especially when it comes to being on the Internet.
If you are shopping for a new computer Windows 8 is not the horror story many are making it out to be. Yes, there will be a learning curve but at this point you'll experience a learning curve whether you decide to go with Windows 8 or Mac or a tablet or a Chromebook or anything else. Unfortunately where every operating system is going through big changes all at the same time there is no way to escape having to learn somethig new all over again.