The only way to 10.7 on the Macbook Pro is to puchase it from the Mac App Store, or purchase the USB key stick from the Apple reseller.
If your Software Update on your 10.7 machine is corrupted either by the Malware, or some third party system modification tool, the best way to get from 10.7 to 10.7.3 is using the combo 10.7.3 update. 10.6.8 you can install a Malware protection Java update without having to upgrade to 10.7. To find the updates you need. read this tip.
Do not install any system modification like MacKeeper, Norton, Onyx, Applejack, Macaroni, or cache cleaner tools. These may prevent the system from being able to update properly. If the tools described don't work on the tip, try repairing permissions first with Applications -> Utilities -> Disk Utility, select First Aid, and select the hard drive partition. Then run the combo updater, and the Java patches in question.