However, if you're only going to be camping in 40F or so, you can get started with a pair of military surplus poncho liners. One of them can be used as a topquilt and the other as a no-sew PLUQ (Poncho Liner UnderQuilt). The whole mess should run you in the $60 to $80 range, be lighter than that 0F synthetic you have, and be less bulky overall to boot.
Now, this is not a permanent solution, but it works for most users down to 45 F or so, and can be supplemented for cheap with a sit pad and a fleece throw from WallyWorld (~$2). Those and decent sleeping clothes should net you another five to ten degrees. Add in a hot water bottle, and you could potentially get down to freezing or just below. It ain't pretty, but it's cheap and relatively light.
If you have a sewing machine (or know someone at college who does and owes you a favor), there's a sewn version of the same underquilt that, if you add a layer of cheap insulation like InsulBright (~$12 to ~$16 at WallyWorld or a big-box fabric store for the size you'll need), should be good down to freezing or so. Now, there you start running into the issue of the PLUQ weighing more--and especially taking up more space. So, that may not be something that you want to do.
As far as weather protection, if you're going to be hiking in 50F or above, I'm a big fan of the GI ponchos: they're nearly indestructible, cool in hot weather (compared to a rain jacket anyway), can be used as a ground sheet for when you get out of the hammock or an improvised Grizz Beak if the weather gets particularly bad, and replaces the need for a pack cover on anything below about 70 liters. Those will run you in the $20 to $30 range at the surplus store.
Feel free to PM me if you have any questions! Oh, and welcome to the madness.