I have PMDG B737NG version 1, how can I upgrade to the current version, short of having to buy the newest version?

if you just bought the 737NG you already have the latest version. If you Do have version 1, just d/l the update in the download section for 737NG's on the PMDG website. Upgrades do not cost anything. Also, you must sign your name to any posts you make here. This helps PMDG from giving support to unregistered (pirated) copies of their software. -Adam Harmon

If you are talking about the 600/700 only some features will be added with the stated upgrade. If you purchase the 800/900 then additional features will be added to the 600/700 as well such as additional FMC items and TCAS for the ND.I would follow the posted advice of installing any applicable patch as noted on the site and it does not give you the functionality you want consider purchasing the 800/900 upgrade.Be sure to follow the order of installation described.