ok when you boot ubuntu off the cd and it loads just click the "install icon" ont he desktop. this will ask you questions and then take you to a partitioner. click manual option and then select the unallocated (your part of the disk that not formatted) and add a 8gb root, a 20 gb /home and a swap that is double the size of you RAM (if you have 2 gb or more just make it 2bg). the rest of the free space you can format to fat32 and share it with windows and linux (format this from the install process too). its really pretty straight forward once you start to see it in front of you, im sure you wont have any problems but you should back up you data in windows just in case.
also the bootloader will automatically install so when you turn on your computer you will have the options of ubuntu or windows.
as for you wireless card it should work i think but once you are into your new install of ubuntu you will have to see. if not you still have windows so any files you need you can download with windows and put them on the fat32 partition, a flash drive of cd to get them to ubuntu.
good luck and dont let it be to scary because its very simple and will be fun for you i think