This is how I started in the industry: entry level winemaster. Yes, there are plenty of grunt work tasks around a winery, but there are many other things to learn by doing cellar work too. Things that come second nature to me, like chasing wine and filling a hose, are not necessarily intuitive types of procedure. There is also quite a bit that can be learned in a true production facility that will never be taught in school. My training along side of one of the top winemakers of this area was priceless, but other connections I was able to make (including meeting my wife!) have been even more valuable.
I'd recommend just contacting the winery you'd like to work for and start with harvest help. Most wineries will hire extra people during crush. I can recall doing 12 hours of hard work and then hanging around the winemaker's lab 'til the wee hours of the morning. By the following crush I had been promoted to cellarmaster and did a lot more machine operation than tank cleaning.
And, by the way, you probably know, but just in case; it's spelled oenology, not oneology!
clyde