jlmedia, the guy they sent was a salesman. He sold you more gear that you didn't need. Take the new stuff back.
You solved the problem right? So you don't need a gate, I thought we figured that out. A gate is just not necessary for your recording studio applications if your gear is set up correctly.
The bit about going direct into the sound card and bypassing the mixer is legit advice. That is certainly one way of doing it. However, at that point what you need is a better sound card, not a gate.
That's really what you need to be saving up for now: a better soundcard. Take the Samson s-com crap thingy back, get your money back, and start saving for a good soundcard. Don't let the salesman talk you into a 60 pound soundcard that you can afford today--save up and get something a few cuts better.
I can't emphasize enough that you are on a path right now to waste extraordinary amounts of money on crap studio gear. You don't need a lot of gear to do what you want to do, you just need a few pieces of *good* gear.