If I have Version 1 of the PTB ABA Study Manual based on the 5th Edition Task List, do I need to buy Version 2?

No. You can purchase Version 1 Updates and Corrections which contain the minor changes included in the current version, as well as updates to the ethics section to reflect the changes announced by the BACB® after the publication of Version 1. These updates come as a downloadable PDF and can be purchased here.