Using existing gas connection for new gas range?
I would call this a very simple job, if you can change a car tire this would be easier.  The basics are proper sealing compounds or tape at the joints, usually 2 adjustable wrenches or a pipe wrench and an adjustable wrench are the only tools needed. And last a bubble leak solution to check the new connections. 

Some fittings use special pipe tape it is yellow or an approved for gas pipe dope going from pipe to the flair fitting.  After leak checking your fittings I will literally a match at a burner and turn it on, it may take a minute for the air to be purged from the lines, once a burner lights I do the others and the oven. I do the oven last because many of the ones I have had use a hot surface ignition and I like to reduce the amount of time that is firing. 
It really not difficult at all. Using the proper gas rated flex pipe and make sure the fittings are the correct size is critical. Depending on your connection to the gas system you may not need any sealant at all. It could be flair fittings then being clean and following the instructions like hand tight and 1/4 additional turn then checking for leaks. It is quite simple but some basic safety checks are important.