No you don't need a whole new system.
Most likely the throw out bearing, clutch disc and pressure plate will need replacing. Parts can run up to $500 depending on make/model. Figure 5-7 hours labor. Why is it slipping? Maybe the master and slave cylinders need rebuilding and that's wicked inexpensive. If you have any mechanical capacity you could do it yourself (the cylinders not the clutch rebuild I don't think I would do the rebuild and I am an excellent shade tree mechanic). I don't know what you're driving so is that worth it? As Click and Clack the Tappet brothers say: a car repair is cheaper than car payments 
I'll add I usually figure $3000 for a tranny repair. This is less than the tranny but still the tranny is involved. Second to resurfacing the flywheel.
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