BZ:
We all have been in that situation at one time, usually more than once. Why the scolding?

You will also be limited by the output of either machine. Get lot's of scrap to start on, you'll need it. Sharpen plenty of extra tungsten.
Books maybe?

Have you ever Oxy-Acetalyne Welded (OAW)?
It's basically the same principal except with TIG you are using an electric heat source rather than flame.
I.E. - you apply enough heat to the surface of the base metal to create a molten puddle with one hand and then you apply filler metal to create a bead with the other hand.
Of course this short explanation is drastically over-simplified as the trick is knowing how to set up and operate the equipment utilizing infinite variables for unique applications while performing delicate, ambidextrous, hand-eye cooridinated movements.
Practice makes perfect (as long as you are more coordinated than I am).
Your equipment manufacturer can supply you with operating instructions and reccomended variable settings for various materials and thicknesses.
There are many choices of educational materials available for you to research/study.
Also, I'm sure the is a Vo-Tech school somewhere near you where you could take some classes and get advice. You might consider this option prior to buying your equipment so that you'll be able to best decide what you need to for your expected applications.
Good Luck!
Tim

some colleges have separate classes for the different welding processes: stick, mig, tig, flux core. I'd start w/ the stick class, since it's a pretty versitile and portable process. also, if you get in good w/ the instructors, they could actually show you the basics of how to mig and tig without taking the mig and tig classes, and you can take the ideas home to play w/ on your own machines. most of the time the best way to learn is by watching somebody else. spend the $500 or whatever it is to take at least 1 class...it'll answer a lot of the questions you have.

I'm in the same boat as you. I have done some limited mig welding on regular carbon, cold-rolled steel, but never any stick or tig welding. As far as a machine, I am leaning towards the Lincoln 175 at this point. I haven't called anybody at our local college, but have looked at the schedules. There are at least two or three classes that are prerequisites for the tig class. Perhaps I could get in a tig class for no credit, which I don't care about anyway. My next option is to call one of my buddies that co-owns a large welding shop and see if I can just come over and look over someone's shoulder for a while.

I purchased a Lincoln Squarewave 175 Pro a couple years ago. It's a real nice machine for a small home/race shop. I drag race and use it on my own car as well as other small projects.

I had zero amount of experience with Tig when I bought this machine. A good friend had a much larger Tig and I had him do my welding before I had my own machine. He was going to come over and give me some lessons, but he was always busy, so I simply took the time to learn and practice myself. I looked around for a local community college to take some courses, but the program was dropped several years ago. I hope some time down the road to take a course or something, once I have free time and the funds to do so. At this point, when I run into a project, I simply take my time and am very attentive to my technique & settings. I'm certainly no expert, but have aquired the basic skills necessary and now need practice and an instructor to move to the next level.

At this point, all my welding has been mild & 4130 chromoly steel. I hope to try some aluminum in the near future.

If you have the funds and the interest, go ahead...buy the machine and have at it...it's frustrating and great fun all at the same time:).

I know the feeling and have had the same questions. On this board or the Technical section, you will find some posts where I received a lot of great help about Al and Stainless GTAW technique. This site is a virtual course on welding. Some people are even kind enough to look at digital pics of work for critique. Look through the old posts and ask questions, then go practice - you'll make progress. There are some good books too. A favorite of mine is Gas Tungston Arc Welding by William H. Minnick. It is available on Powells Books web site or likely any other bookseller.

I have a Miller Syncrowave 180SD and really enjoy it. Apparently there is a new version coming out with some additional adjustments. In a class that I'm taking I am using a Miller 250 which has more power, range and ways of adjusting the arc characteristics -- but that is a much more expensive machine. I have not used the Lincoln 175 but have never heard complaints about it.

I suspect that you will go through "what is the best helmet/autodarkening lens etc" thought process too. Be careful with some autodarkening products. They don't all work well with Tig, especially at low amps. Lots of posts on that subject too if you care to look.

Crazy as it may seem, I find it relaxing to sit down with a soft DC arc on some steel and just practice welding.
Ken