Install txt file along with Air app

You can embed any kind of assets with Adobe AIR, so a txt file sure no problem.

You can use Advanced Installer but you don't have to, there are many other solutions: NSIS, Inno Setup, Wix, etc.

Now for the part "without recreating the AIR application each time", you may need to rethink that.

Technically you can build an AIR app and not change the source code and only update a config file,

but you would still want to recompile the AIR app each time, so you can increase the version number.

In fact, all that depends on what you try to do, which operating system you are targeting (so far I guess Windows)

and how much professional you want the app and/or installer to be.

The simplest of all would be to package a Windows AIR app as "native", it will produce a vary basic exe installer for you.

A more complex solution would be to produce a Windows AIR app as "bundle" (which embed the captive runtime),
then use something like Wix to produce a .msi installer for Windows 7 and 8.1 and 10, and also produce

an appx installer for the UWP, and also use a code signing certificate to sign all those installers and executables.

look at the doc Developing AIR applications for the desktop