If your vehicle is front wheel drive and has an automatic transmission and you have moderate mechanical skills, it should take you about 8 to 10 hours to replace the transmission. If your vehicle is a rear wheel drive vehicle it should take you between 5 to 7 hours to replace the automatic transmission.
Replacing a transmission in any vehicle is a fairly time consuming project. The actual time it takes really depends on an individual vehicle, however, the average time to take one out and replace it with a new or refurbished one takes approximately 2-5 days on average.
IT all depends on what you know and how fast you are, and if you have the right tools. it takes me about 3 hours to pull and put one in(replaced about 15 trannys)and about 5 hours on a fwd. It may be a bit longer on the newer cars and trucks.
It would help to know if the transmission is manual or automatic. At any rate if you are a good mechanic one day. If a not so good mechanic figure two days.