Yes, you'll need a router.
There are hundreds of models available but make sure you get one that's for cable (ethernet) rather than ADSL (RJ11) such as those listed
here on BroadbandStuff.
For £40 even VM will supply (and more importantly, offer support for) a decent
Netgear wireless router.
In my experience of using a similar setup, QOS isn't necessary but should help improve the quality of calls while you are downloading on your pc.
There are combined cable modem/routers but they are not supplied or supported by VM.
Oh and don't worry about asking what seems like 'dummy' questions: we all have to start learning from somewhere! And every 'expert' here, was a n00b at some point.
hth