Tying nymphs in a couple of different weights is a good idea. Learning to cast a heavier nymph is not a long learning curve, you sort of lob rather than cast because the nymph, being heavier does offer more resistance to change in direction when you are casting.
YouTube - The Nymph Cast
This is not exactly what I mean but it is a good technique to use when czech nymphing or when using any heavy nymph. Typically a short line and a "lob" rather than a traditional cast. There may be better video clips out there if you have a look around.