Well, how much are you hoping to get a Superdrive for? $100? Probably $150. So you want to void your warranty and diddle with your system for $50 in savings?
If you really must save, it may be worth considering buying an external DVD writer. Apple supports them now with iDVD. They are cheap. They are faster than internal drives. You can get them with the lightscribe option which seems kinda cool. Obviously you sacrifice portability.
Some upgrades from Apple are too expensive (RAM - 2 gig for $400 give me a break; and 100GB HD to 120GB HD for another $100 puhlease) but I don't think the 1.83 to 2.0 is really much of a savings considering what you get for it.
I know that doesn't answer any of your questions, and maybe you've thought all this out and I'm just being annoying - so if so, apologies.