Musicians (Guitarist/Voice Folks), Need Some Help

Getting up in years (74) but recently decided to pull down my Takamine 6 string and do some picking.

What I need help with is the following:

After I transpose the chords into a key I can sing, where can I get a setup which will record the song and then play it back, say, in the key of A which will then act as my guide?

Is there such a thing and how expensive is it? Also it needs to be idiot proof (me).

If any of you can help, I sure would appreciate it.