My advice is "don't".
Campagnolo doesn't typically play nice with non-Campy stuff without jumping through hoops (see footnote). In particular, Shimano cassettes (which you need for <=10 speed systems for Shimano shifters) won't go on a Campagnolo freehub. So, you need to either move completely to Campy (expensive) or buy a rear wheel which is Shimano compatible. A 11 speed Shimano comaptible freehub will take an 8 speed cassette with some spacer(s) thrown on. Most <11 speed Shimano compatible freehubs will not take a 11 speed cassette since they are too short (exception is some Mavic ones).
[Zinn has found that the 11 speed stuff plays OK with each other, but Sora isn't a 11 speed set]
I'd personally recommend getting a wheel (if you had to) which has a Shimano compatible freehub on it. And for what its worth, 8 speeds is plenty - you may want a different cassette in the back or whatever, but you'll get a lot more gain if you become more fit [you may also feel faster on a racier bike; given that wheels are one of the most expensive parts of a bike (along with the frame and shifters), you may just want to upgrade to a whole new racier bike ]. For this reason, I'd say if the wheel is working, don't bother replacing it (or if it isn't and it needs minor repairs, e.g. truing, get that done and go ride).
Footnote: I understand there are hacks such as JTek Shiftmates for interfacing Campy wheels+hubs with Shimano shifters and what not, but this is not an ideal option [and I don't know the entire Campy compatibility ruleset, so I choose to ignore it]. There are also freehubs which have parts which can be swapped for switching between Shimano and Campy (made by Mavic), but this is also rather expensive.
