Hi and welcome. You are correct that the people here are very knowledgeable and willing to help.

If you have the money spend it. The benefits of buying from the Local Bike Shop (LBS) is that they can help you with fit (size and type of bike), and when things go wrong with the bike (flats, cable adjustments)

You can save money buying used on craigslist, but you have to have some knowledge of bikes to know what you are looking for. Sometimes a friend that is a cyclist can help in this department, or you can post what city your in and people on the forum will look at craigslist in your area and recommend a bike. Still you need to have some basic understandings of bike workings.

For me as a totally clueless bike rider, I went to my local LBS, and they recommended a certain model and size (Fuji Absolute 3.0, 56 cm), and I bought it for around 500 dollars. It was sticker shock for me also, but it was totally worth it and I've ridden approximately 20, 000 miles on this bike with no major problems.

Slowly through reading this forum and getting a few books, I've learned a little about bike maintenance and such, and bought a rain bike from craigslist that I maintain myself. I still go to the for adjustments to my Fuji, or to just talk to the owner who is a great guy.

By establishing a relationship with the owner of the LBS, I can usually take my bike by there and he adjusts it while I wait and drink coffee.

Long answer I know, but I would say, pay the money and start riding, and very soon learn about gator skin tires and buy them