Welcome to the forum!
There are varying opinions on this forum (and elsewhere) regarding the best file formats and best software to use when converting CDs. For me, iTunes works just fine. It has an option to "Import CD and Eject" when you insert a CD, so it makes the process pretty fluid. If you have two optical drives, all the better. I haven't done it in years, but I used one of the higher quality formats and was happy with it. Well, until my hard drive crashed and I lost them all.
So...my advice is to have a backup copy of those files.
After you spend all of the time to load 300+ CDs into a drive, it makes sense to copy those files onto a second hard drive. I wish that hard drives were as cheap as they are now back when I did it.