Second, since the capacity of SSD's is relatively low (100 to 120gb is my budget), I will need to install some programs and games (specifically STEAM) on another physical hardrive. My concern is updates and patches on programs like MS Office, and games under STEAM. Is it problematic to install programs on another drive?
Nope, that works fine. I have Steam on my storage drive, works just the same as if it were on any other drive
I have MS Office on my C: drive, though I do think that you can't fully install it to a different drive, it still puts stuff on your C: (about 1GB).
Third, if installing programs to a separate drive, will I see a performance increase if using a WD 150gb Raptor or a couple Seagate 360gb in RAID0?
Yes, you'll see a performance increase by using a performance drive, or RAID0 them. That's the point :P
(I dunno about TRIM, I'll leave that to someone else)
Just a note - my setup is an 80GB drive, split into two 40GB partitions, each with their own OS on. Each of those partitions, assuming I remember always to install to my storage drive (640GB), rarely goes above 25GB used - I moved the My Documents/Music/Pictures/Video folders onto my storage drive too.
It's a lot easier to keep the OS drive clean than you'd think. I would recommend that, instead of going for a 100GB+ SSD, go for a faster 60GB one, preferably an Intel X-25M. It will cost about the same but performance is awesome.