Lost 3rd gear

So I recently blew a line on my 05 1500 5.7 4x4 and upon repairing the line and topping fluids it hasn't regained 3rd, torque converter is also occasionally problematic as it'll stall out upon warming up when placed in gear, the transmission is obviously upset with itself, I'm only wondering if it's more worth it to attempt a rebuild or go after a new one to swap, it's outside my realm of something I want to tackle, I don't have the facilities currently, but I'm wondering what's a better angle to approach from, as far as data goes it's only throwing me a p0700 code, anything I should check to possibly tell me more before making a decision? The current engine/trans both have 180kms/111k miles if that is at all helpful.
Any feedback is appreciated, thanks!