In regards to your 1st Q:
5400RPM drives can be significantly slower than 7200RPM drives. Just check the average seek times under their specs to see the difference. Also, some 5400RPM drives aren't ATA/100 compatible, meaning that if you place them on the same cable, the faster hard drive might be forced to run at a slower spec (like ATA/66).
In regards to your 2nd Q:
No, you won't have to partition the 60GB drive. You could simply install it and load windows which will just list it as your D: drive (assuming the drive letter D: is available).
However, I recommend that you do. Why, you ask? In the future when you want to defrag it, it would be a lot quicker defragging a 15GB partition versus the entire 60GB hard drive all at once.
Hope that helps...
~cdogg