Riding Mower Won't Start. Please Help!

I have a Husqvarna Lawn 'Tractor' with Kohler engine. I bought it in 2008 or 2009. I used it fairly regularly the 1st year or so. It sat in the garage untouched the 2nd half of summer 2010 and hasn't been touched since - until today. (I was sick during that time, so I hired a landscaping service to handle the lawn.)

This morning I replaced the battery which was dead after sitting unused for so long. The gas tank was empty, the gas having apparently evaporated while it was sitting up. Before I got sick I did the yard work, so I always kept a container of gas on hand in those days. Without really giving it any thought, today upon realizing the tank was empty, I reached for my gas can and poured it all in, filling the tank about 1/2 way. My best guess is that the gas was a 2010 vintage (but that was a good year, right?). And, yes, I did 'saddle up' and turn the key...The engine took a huge gulp of that antique gas, roared to life for a moment - and then before it had time to 'even out', it promptly fainted, refusing to start again. Since then, it has basically been in a coma. (sniffle, sniffle, honk)

Before I go on, I'm thinking I should reveal that I'm a female - in case that wasn't otherwise evident from my description of the situation (lol). While I have a decent knowledge of electrical systems (I'm an electrical engineer) including some practical experience as a elex tech early on in my career, my knowledge of mechanical systems is very limited, and I just totally don't get the whole combustion engine thing at all. Whether it's a car or a lawn tractor, all I know how to do is put in gas and turn the key, oh, and cry when something goes wrong. Just thought we should establish my relative knowledge of the situation (or lack thereof) before continuing.

So, now back to today and the mower. Realizing that I probably shouldn't have fed it old gas, I then siphoned the gas back out of the tank (and into a container to take to the recycling center). I also purchased new gas, premium to insure it met the higher rating recommended by the manufacturer. I have not put the new gas in the tank yet, nor have I tried to restart the mower. I decided to take a break and ask for advise before doing anything else. (Too bad I didn't think of that sooner, right?) Just in case I need to do something else before I put the new gas in, I wanted to ask for instructions before proceeding - basically, I don't want to have to siphon gas again if I can help it. Let's just say that siphoning gas was a less than pleasant experience.

So, anybody out there with experience in this department have any suggestions? Should I put the new gas in and try to start the thing? Or did I ruin it already by trying to start it with the old gas? (No problem, it was only a $2k machine, hardly used. sniffle, sniffle) Should I do something before I put in the new gas? Let the tank 'air out', maybe? Or should I call Lowe's to send someone out to get it? (Before you say, 'yes' to that last question, please note that I'm currently jobless and broke. I may have to let them fix it, but I probably can't afford to do that right now, not if I also want electricity, water, and food, that is.)

So there you have it. The weeds in the front yard are getting pretty high now, and I must get them mowed asap, before the HOA starts fining me. Did I mention the no job part? I have a nearly new but neglected mower with an empty tank, and I have a container of newly purchased, premium gas on hand. Should I pour it in the tank and try to start it? I really need some input from someone with knowledge/experience working with this kind of engine/machine. Please help.