You might as well contact Lenovo support and/or the dealer you bought the laptop from, and determine what they might offer as an upgrade from Windows 7 to a customer. Its at least worth a try.
Lenovo Support: http://support.lenovo.com/us/en
Lenovo Forums: http://forums.lenovo.com/
Lenovo Upgrade to 8.1 advisory: http://support.lenovo.com/us/en/documents/ht079684
Lenovo Upgrade to 8.1 FAQ: http://windows.microsoft.com/en-us/windows-8/upgrade-to-windows-8
Here is an eBay offer of a Windows 8 "Lenovo Windows 8 Pro/App Drivers Recovery Disc set/Upgrade to 8.1 (13355-402D". If you could somehow install this over Windows 7, you might then be able to get a free upgrade to Windows 8.1. Probably a bit chancy though. Can't guarantee results but the cost is $14.99 plus $3.84 shipping. You might check with Alan on this. http://www.ebay.com/itm/Lenovo-Windows-8-Pro-App-Drivers-Recovery-Disc-set-Upgrade-to-8-1-13355-402D-/271660882282?pt=US_Operating_Systems_Software&hash=item3f4040196a