[RESOLVED] Advise on Installing Logitech LX8 Mouse

Today I received the Logitech LX8 Wireless, Cordless, Laser mouse that I had ordered. The problem is that it arrived just as my husband had to leave to go to work and he won't be back home until about 4 AM from work. I am so excited about this new mouse and want to start using it right away. My husband is the techie in our family so I have never hooked up anything to our computers before--he always did everything. There was no software with the mouse and instructions were not real plain to me. This is what I have. I have a Dell Inspiron 531 with ports in the back and front. I have a second hard drive, external, on the port in the front. I presume all of these are USB ports. It looks as if my husband has my MS optical corded mouse plugged into the back of my computer. My computer sits in a cabinet below my desktop. The desk (very large desk) is sitting almost flush to the wall. I understand the directions about how to install batteries and how to power the mouse on, but what I want to know is what do you do first? Don't I have to unplug the mouse that is already installed before I install the new mouse? I did a lot of Internet Research trying to find exact instructions on installing this mouse and according to one thing that I read, once you power this mouse on it takes you straight to the Logitech site to download the software for it. If I download the software for it, does it instantly install the software to the mouse? I guess what has me confused is that if the new mouse does not work until I download the software, how will I get on the site with the old mouse and have the site to install the software to the new mouse? If the site will just let me download the software without installing, then I guess I could use the old mouse to download the software. I am not tech minded when it comes to hardware (my husband is), so I don't know if the software is installed to the computer itself or to the mouse? Does anyone have this mouse and could give me step by step instructions for installing it? I know that I will probably have to use the USB extension stand that comes with it because of where the computer is located.
I am using Windows Vista.
Thanks,

You can keep the previous mouse installed, as well as the new cordless Logitech.

Or just unplug the old mouse and replace with the new one. You may not get the full functionality until the Logitech drivers are installed, but the basic mouse functions will work just fine.

Went to bed last night before getting any replies, but husband woke early this AM & installed mouse for me. Amazingly I did not have to go to Logitech's web site and download software as was led to believe by customer's reviews (read on another site). Was able to configure the mouse in the Control Panel. Puzzling was that the mouse it showed me to configure was for my old MS Intelli Optical mouse. Even so, by changing the settings in the Optical Mouse software, it allowed me to change my Logitech mouse --even all the buttons now work on my new mouse! Computer must have been fooled into thinking that the 2 mice were the same! I love my mouse, just have to get use to the pointer moving so fast! Have slowed it down in the Control Panel but think I may need to slow it down even more.
Thanks for all the advice.