Hello,
Inventory Service is just a service for use by other tools. Does it have a DB, actually I am not sure. You may have to contact VMware for that one. If you installed the Inventory Service on another VM and not vCenter (which is recommended) then you may loose vCenter inventory access from other subsystems (such as VIN and VSM) but not vCenter. I have not tested this type of failure myself. You may wish to test this in a controlled manner.
Generally if you are reinstalling vCenter you may be reinstalling these other services as well... That depends on your configuration.
Best regards,
Edward L. Haletky
VMware Communities User Moderator, VMware vExpert 2009, 2010, 2011,2012,2013,2014
Author of the books 'VMWare ESX and ESXi in the Enterprise: Planning Deployment Virtualization Servers', Copyright 2011 Pearson Education. 'VMware vSphere and Virtual Infrastructure Security: Securing the Virtual Environment', Copyright 2009 Pearson Education.
Virtualization and Cloud Security Analyst: The Virtualization Practice, LLC -- vSphere Upgrade Saga -- Virtualization Security Round Table Podcast