Yes, and if you have installed WVD2008 on your server :-), you probably have the Framework already. But yes, essentially installing Framework 3.5 is enough (since you already have v2 on your server).
See the link I posted, it has good explanation on the Framework's versioning, which is confusing. Point is that in ASP.NET 3.5, ASP.NET itself hasn't upgraded that much so it is basically still v2.0 SP1.