Technically I don't think you need to uninstall K2 2003 if you don't want, however you'll want to make sure that the K2 2003 service is not running (disabled) as by default it, and blackpearl use port 5252 for workflow processing. However, if you have no need for K2 2003, you should be able to uninstall it before installing blackpearl.
As for blackpearl prereqs, I would recommend you refer to the K2 blackpearl Getting Started Guide available for download on the portal (https://portal.k2workflow.com/downloads/bp/Default.aspx). It is highly recommended that this be read for pre-requisites as well as installation instructions.
HTH.
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