How much would changing to Linux affect my computer life?
There is a lot less for gaming options in Linux, but there are certailnly games and I suppose with VMWare you could run Windows games. But almost all other functions you would do in Windows, you can do something similar in Linux.
Is it anything similar to Windows at all?
Things different :
Linux uses a different file system (not NTFS like XP and Vista). Linux usually uses ext2 and ext3 file systems, which is a different way for the OS to read, write and archive files to the HDD. In other words, the heirarchial design of Linux is based on the concept that everything comes from the "root", which is where administration priveleges are based from.
Things same:
There are programs like OpenOffice which is similar to the M$ Office Suite. The Terminal offers a text-based interface for making system changes, installations, etc. Sort of like the old DOS prompt window. There is a plethora of Linux programs you can download, all free and many are like Windows programs, but of course they aren't though.
Would my current PC games be compatible with Linux?
Not likely.
*Advice: Give Ubuntu a try, it is relatively easy for n00bs to Linux. I haven't been using it myself more than a couple months, but it has been worth the time invested thus far, and then some.
**More advice: DONT get into the habit of thinking it should be just like Windows, it isnt Windows. Things will seem weird, but the challenge to me is exciting. People like Saxon have used it all their lives, so they are the ones who can help you more on this. Hang around this forum and you will learn a lot right away, there are a lot of very knowledgeable people around these parts.