What you want to do is very possible for sure. And there are many ways to accomplish it. It's hard to say which is the best way in fact cuz there are so many and 10 people will have 20 opinions on it. I'll just tell you what I do and you can do with that whatever.
If you're gonna do it all on computer, you need a base program to do MIDI sequencing in and audio recording (and a decent sound card, of course). I use Cakewalk Sonar myself, there are other options. Cakewalk Guitar Studio is easier to use and much more affordable than full-blown Sonar. For sound samples i use Soundfonts and run them with LiveSynth Pro. I used an SBLive to host the Soundfonts for a long time, which also works fine. There are other options here as well like Gigastudio (expensive) and Vsampler.
Once you have the basic setup it's just a matter of learning how to use the software to do what you want to do. You'll probly need a decent
MIDI controller keyboard to input keyboard parts, bass parts, or even drum parts. For drums, for example, i use a KAT DK-10 which you actually play with sticks. This is very handy if you know how to play drums.
Wow... there are just a myriad of options especially if you're starting from scratch. There are some really good samples out there, tho, if you go looking for them. If you want an example of a "fake" band, listen to any of my stuff at
www.mp3.com/SilentImplosion or
www.mp3.com/Dichoto (=D=I=C=H=O=T=O=M=Y=, NOT the "other" Dichotomy, good God). The only recorded audio parts are guitar and vocals. All the rest is MIDI.
