During the first few rides on my new Specialized Allez Triple Sport something was out of whack on the front derailleur adjustment and I limped home without a full range of gears a couple of times. It was all completely different from the friction shift levers on my old mid-1960's 10-speed. I got information from several sites on the Internet and got it adjusted so it worked like it should. I also made some notes so it will be even easier the next time. When I took the bike back to the LBS for its 20 hour break-in check up, they did not need to change anything I had done.
I like to make or improvise special tools whenever possible. Even if I have to buy a tool, it will probably pay for itself in one or two uses.
Most of the time I can do a good job of what needs to be done. If I do make a mess of something, I will pay a shop to fix it and will still be ahead over the long haul.