First, don't waste your time or money on Leopard. You might as well go to Snow Leopard which is still supported.
Upgrading to Snow Leopard
You must purchase Snow Leopard through the Apple Store: Mac OS X 10.6 Snow Leopard - Apple Store (U.S.). The price is $19.99 plus tax. You will be sent physical media by mail after placing your order.
After you install Snow Leopard you will have to download and install the Mac OS X 10.6.8 Update Combo v1.1 to update Snow Leopard to 10.6.8 and give you access to the App Store. Access to the App Store enables you to download Mountain Lion if your computer meets the requirements.
Snow Leopard General Requirements
1. Mac computer with an Intel processor
2. 1GB of memory
3. 5GB of available disk space
4. DVD drive for installation
5. Some features require a compatible Internet service provider;
fees may apply.
6. Some features require Apple’s MobileMe service; fees and
terms apply.You will need an optical drive. Buy an external drive. Or if you can borrow the use of another Mac with a working optical drive, then you can clone the DVD to an 8 or 16 GB USB flash drive.
Apple sent me a 10.5 DVD for free and stated my macbook could not be upgraded to snow leopard.
I have a MarBook Pro 15" 1.83 GHz Intel Duo with 2 GB of RAM.
Do you mean buy and external "optical" drive? If so, I will check around at work and see if someone got one laying around and all else fails I will buy one. We just moved and I do not have an extra MAC to use. I wonder if they would get this to work if I went to the apple store for support?
Yes, you can buy an external optical drive that uses either Firewire or USB port or you can borrow one. You can even use another Mac that has a working optical drive by using Target Disk Mode. It's possible they might install Leopard for you, but what happens if you need to use the DVD for other repairs or installations?