New RAM? New graphics card? How to backup my computer? Restore?

I have a Lenovo Ideapad N580. A great computer. Intel pentium, 4gb of DDR3 ram, 2.2ghz dual core, etc. Now I want to upgrade my ram to alteast 8. I have 4 but just one. 4gh stick. There are 2 slots in the computer itself, so one is empty and the other has a 4gb.
So I called bestbuy and they said we can upgrade it, they said they can give me 2 8gb sticks for. 150$.
Couldn't I just buy another. 4gb stick from amazon? I already know how to install new ram anyway.
I was also thinking I should get a new graphics card. Before I buy games, I look at the minimum requirments. I have the stock ghraphics card that comes with the computer (whatever kind of GC that is) and I meet the requirments for everything EXCEPT that. It's terrible. I would really love it if someone told me I could upgrade and to what and where.
Also, I'd like to wipe my computer, but I'm not EXACTLY sure how. I know that you backup the files you want to keep on a USB drive, or even CDs and then wipe it but… I need a walk through.
I also haveIf you good people do answer, can you be sure to be in depth and provide links (for example, getting new ram) or videos (for example, how to backup and wipe)?
Also, if you know the answer only a fraction of my questions, STILL Please ANSWER! It's very hard to find this info!
Many thanks
New RAM New graphics card How to backup my computer Restore

To find what it now has, max system supports, correct memory module(s) for upgrade go to http://www.crucial.com/...rucial.com and enter the laptops info.

You can't upgrade the graphic/video card chip set in the laptop it is made into the mother board and or processor. No one sells a graphic card chip set for a laptop.

Need to know what version of Windows is installed to be of help on reinstall instructions. Do you have or did you create the operating system recovery disc set for the laptop? That or a built in system recovery is all that is needed to reinstall Windows and put it back to factory. You can find the info at Lenovo support by model number and operating system of the laptop.

Lenovo, Creating Recovery Media in Windows 7 http://support.lenovo.com/...MIGR-74040

How do I recover my system using ThinkVantage Rescue and Recovery http://support.lenovo.com/...D=HT002492

Yes, you can just buy 1 x 4gb DDR3.
BestBuy is not your best buy nor do they provide good or great advice. Their advice is based upon how it can help them sell you something, not your best interests. Try Newegg.com instead. Just make sure it is the same speed as what you have. Another option is a site like Crucial.com where you tell them your computer make and model and they will tell you exactly which (of theirs) memory you need/can use.

To clear your machine and start over, look up the instructions on how to perform a factory restore on your model of machine and follow those instructions. BEFORE PROCEEDING be sure to back up your personal files/data as the restore will wipe your machine and put it back to the way it was when it left the factory. To back up your computer, connect an external drive with enough space available for your data ad files, then use the Microsoft Easy Transfer wizard and it will back up your files and settings to the drive.

You can't upgrade the graphics card in a laptop (with a very few exceptions). You might be able to upgrade the processor, but to limited benefit.

Yes you can buy another 4GB stick. That will give you 8GB, and since you will have 2 matching sticks, it will run in dual channel, increasing memory bandwidth. And in turn will increase performance of your integrated graphics.
16GB would be useless, as you won't ever even use 8GB:/

But even with 8GB of memory in dual channel, it still won't be very good for gaming at all.
you need a decent gpu to play games, and laptop are not upgradable, meaning the only way to get a better gpu is to buy a new laptop. (or better yet a desktop)

google
"how to re-install windows" or something
its not that hard to find guides on how to do it.