No, I haven't done that, but I guess my first question is, do you now what's wrong with your current A/C unit? I usually opt to repair than replace, if economically sound. Sometimes all they need is a new relay or cleaning to become functional again. I had to replace a relay on our front A/C around the 10 year old mark, and it's been working for 9 years since.
I know there are members here who have more experience with the A/Cs, so I'm sure they can give you more opinions about changing out the unit, if that's what needs to be done.
Good Luck,
~Rick