Sell my LJ and buy a TJ?

Sounds like my wife is a little different than your wife, she gave me the green light on a new gladiator after she test drove one. We priced out what we would want and both said no way, could not justify the price. That’s what got me thinking about a good condition TJ with an automatic, that and the obscene prices I have been seeing LJ’s selling for. She doesn’t really need a daily just something to get to the store a couple of times a week. As much as I like a manual I could live with an automatic as our daily driver with a beater for me to use if she should want to go somewhere.
As someone who owns both an LJ and TJ (automatics), keep the LJ. I swap back and fourth between daily driving both and as much as I love driving the TJ, the LJ is just more useful. Especially if the wife will be using it to run errands. With the back seat folded up or removed, there is considerable usable space available.

Since you have a nice low miles LJ, have you considered finding someone that will do an automatic conversion? There are people here who have either done the conversion themselves or taken it to someone that did it for them. The most economical way to do this though is to find someone with an automatic that wants to swap to a manual. Those folks are out there, but you'd need to post a wanted thread to see what interest you'd get.
 
I had both as well, an 06 TJ Unlimited with a 6-speed and an 03 TJ standard wheel base with an 4-speed auto. I was faced with the same conundrum and ultimately sold the Unlimited and kept the TJ. For me it was a tough choice, but keeping my TJ allowed me to keep wheeling how I like and to build the Unlimited or swap parts between the Jeeps was not worth the cost or time for me. I miss the 6-speed behind the 4.0 in the Unlimited, but the TJ is geared low enough that the auto bothers me on the street with 35s.

Make the choice that best fits your lifestyle and allows you to do what you enjoy. If your wife likes riding with you and not driving, then it doesn’t matter what trans you have. If she’s dropped hints about wishing you had an auto so she can drive, sell the Unlimited and buy a Jeep with an auto transmission so you can both get behind the wheel. Good luck with your decision, when I sold mine a month ago it lasted less than a week and I got asking price. Clean it up and see what kind of traction you get.
 
No idea the cost, could you convert it to an auto?
If you can get good deals and do all the work yourself, not have to rebuild the transmission, etc...its about $1000-1500 to swap the auto in place of the manual. I have all the parts sitting on a shelf ready to go...so I'm familiar. I'd bet the swap could hit 3K easy if you need to rebuild the transmission and/or pay Ebay prices for the parts you need.