would pay to upgrade imo; been many improvements since LR2.
as for learning; I always suggest to get a book like Scott Kelby's. After you get your head around the important parts you can use Google to find anything you need more help with. Julieanne Kost. Principal Digital Imaging Evangelist, Adobe Systems, Inc. Adobe Lightroom tutorials is worth look up.
I bought LR in June, 2012, when I purchased my computer. I never used it then as a film shooter, but have recently gotten my first digital camera and lenses and am ready to start learning. Is there viable training available for me with my older version 2.7? Also, if I opt for a monthly plan is the financial commitment actually month-to-month?
The Photographers Plan for subscription ($9.99 per month) includes Lightroom and Photoshop and I understand you could pay annually or monthly..... you never pay for upgrades again as it is all inclusive.
Otherwise as IanB suggests you could just pay the Upgrade price which will leapfrog you straight to the current version. But next version e.g. Lr6 will require another upgrade cost.
AdobeTV has great free tutorials or Lynda.com for paid are my suggestions.