I've been on testosterone for a couple years now and did a ton of research before making the plunge. I'm in my late 30's, btw. Here are a few points:
Insurance will generally pay if your doctor says you need the treatment. Most doctors follow a rule of requiring testosterone levels to be under 300. HMO scenarios may have stricter guidelines (Kaiser requires <240). The blood draw to test is quick and easy so if you're thinking about it, you might as well get the test done.
Don't plan on ever being on and off Testosterone. Whether or not it works out this way, consider it a permanent choice. If you go off, your levels will plummet and you will be very miserable until they go up again and that could take a while (and may never go back up to pre-treatment levels).
There are various forms of application including gels, creams, patches, injections, etc. Injections come in generic form and are the cheapest option if insurance isn't on your side. Many patients prefer injections, especially if they're allowed to self-inject at home.