How much would it cost to make a Toyota 4runner from a 2wd to 4wd? ?

[Payam K]

I just got a Toyota 4runner 2006 it was my fathers car given to me when he passed away its a 2wd. It has a lot of value to me my brothers and we do a lot of out door activitys together like camping, glamis, pismo stuff like this and we would like to take the 4runner because it like we are bringing a him along with us I really want to make it a 4wd but don't know where to start how much it will cost and if possible at all thank you for your time g-dbless