You can still upgrade to OS X 10.7 Lion.
system requirements for OS X Lion and Mac OS X v10.6.
OS X Lion system requirements
To use Lion, make sure your computer has the following:
- An Intel Core 2 Duo, Core i3, Core i5, Core i7, or Xeon processor
- Mac OS X v10.6.6 or later to install via the Mac App Store (v10.6.8 recommended); you can install without Mac OS X v10.6 by using an OS X Lion USB Thumb Drive, available on the Apple Online Store
- 7 GB of available disk space
- 2 GB of RAM
If your Mac does not meet these requirements, you will need to upgrade your Mac before installing Lion.
You can purchase an email code to download and install Lion from the Mac App Store.
I would advise installing more RAM into your MacBook as versions of OS X after Snow Leoaprd really require, at least 4 GBs of RAM.
Your MacBook year and model can take a total of 6 GBs of RAM.
I'd advise purchasing and installing the full 6 GBs of RAM.
Correct and reliable Mac RAM can be purchased from online Mac RAM sourceOWC (macsales.com).
They are the only RAM seller that have the 6 GB RAM kit for your MacBook.
I referenced where you can find the 6 GB RAM Kit for your MacBook.
OWC (macsales.com). Apple is NOT going to have your RAM for your Mac. And even if they did, they charge 3 times the price for it!
Find your MacBook Model and RAM and the 6 GB RAM kit here.