About Tools for ITIL V3
You never have to buy any tools: any process can be operated manually. But they help. Not only has ITIL version 3 expanded into new processes, but it has also expanded in another dimension: along the service lifecycle. Think of it as not only has functionality got longer but it has got wider too (see the diagram above).
If you are lucky enough to have picked a vendor who will include all this new ITIL V3 functionality as an upgrade and you are current on maintenance, then you will only need to go to the expense of rolling out a new version when you adopt ITIL Version 3.
Having worked for an ITSM vendor, I'm betting that (a) some of the new ITIL V3 functionality will be extra cost options and (b) parts of ITIL V3 will go outside the comfort zone of some vendors and they just won't cover it - think Service Strategy book.
So nobody needs new tools for ITIL V3 but there is a fair chance you'll be paying for options or additional tools. Look how many vendors managed to make their CMDB a chargeable option instead of a core part of your existing products.
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