1) It really depends. Little Giant and HovaBator are popular incubators for first timers(like me). The price varies dramatically. If you are a busy individual and can't be home to flip the eggs three times a day, every day, then you would probably want to get the automatic turners. I think the Little Giants start at about 70 or 80 and the HovaBators start at around 120 or 130. You can expect to pay an extra 40-50 dollars for the automatic turners. I personally chose HovaBator.. I found it had more positive reviews than the Little Giant so I decided to pay a little bit more. You can find all of these incubators online. Shop around, some places have killer package deals.
2) You can put as many eggs as you can cram into it. Probably 60ish for hand turning. However, if you want to use automatic turners they will both hold 42 chicken-sized eggs and 140 quail eggs. (I noticed in both product descriptions for HovaBator and Little Giant turners it says capacity is 41 eggs. But it's clearly 42.. is there a reason the description says 41? maybe someone knows why?)
3) Temperature you want around 100 degrees. I think 99.5 to be exact. Humidity can vary a lot, temperature is definitely most crucial but water levels is good to track. You can buy addon temperature/hydrometers for the HovaBator for an extra $10. I'm sure Little Giant has something similar.
4) When chicks are inside the shell the nutrients and water they need absorbs right into them. They need no food or water for the first three days but it's probably a good idea to get them into a nice 100*F brooder after they have dried. Be patient.
5) Lockdown is when the eggs don't need to be turned anymore. For chickens that is day 18. For the next three days after lockdown the chickens begin to wiggle back and forth and peep. They'll eventually poke through the shell and be born.
6) I'm still brand new to incubating myself so I'm not sure. I know in the sticky at the top of this forum there is a subject about intervening an egg that is in the process of hatching. I would check there first but from the sounds of it intervention is a last case scenario.
This is a good place to learn about hatching. You can also watch YouTube videos. I have been collecting fertile eggs and I set my first batch tomorrow. Fingers crossed. I think it should be fine, just read read read. I've been recently trying to read the threads with people that are asking for help with their incubation problems. Lot of little tricks and tips you can learn from experienced hatchers that have dealt with every malfunction you can think of. Good luck.