First time ground-up build, a couple questions

[Labes]

Hey, I've upgraded pretty well everything (hard drive, videocard, processor, memory, cd drives, etc) in previous computers, so the only thing I think I'll be alright for the actual building, I just have some questions. My build is as follows:
Gigabyte GA-965P-DS3
Corsair XMS2 DDR2-800 2GB (2x1GB)
Intel C2D E6420
- Scythe Katana 2 CPU Cooler
Seagate 7200.10 250GB Harddrive
EVGA 8800GTS 320mb version
Corsair 520W PSU
Antec 900 case

Running on 64bit Vista Home Premium. I just want to know a few things:

1) I should be able to overclock the 6420 to about 3-3.2 gHz right? I've got some experience and I've heard of around there as well as some people getting alot higher. Are the higher ones just good flukes in the processors?
2) Would it really be worth the money to get a small harddrive just for the OS and then have a main one which I save everything else to? I've seen a few people going with a 50-80GB HD and then a second one of 300+.

Thanks for any help.

Edit: for the extra $120 (canadian) is it worth it to upgrade to the 640mb version of the GTS? I'm thinking I'll be able to run near-max settings until the end of the year, and good video settings for the next few years after that, with the 320mb. Is that reasonable? (ie. in two years I don't want to be running a game on minimum settings, like I am now)

 

[alcattle]

Looks like a good list, assume you already have the rest of the system.

1. e6420 is kind of new so not much info on the max safe O/C, 3-3.2 should be doable.

2. I like have 2 drives, if the OS goes bad, your data will be safe. REinstalls are much easier with 2 drives.

3. What monitor are you using? the 320 is ok up to 1200x1000 then gets iffy on high rez.