If you wanted to do it on your own: EXTREMELY hard if you have never done anything like this. I say that because the engine and trans might resist coming apart and you'll have to not only swap out the trans, but the linkage and pedals and so on. If you decide that you really want to do it though, and have a donor car, it is totally do-able. Really, most things are able to happen if you put forth enough time and effort.
If you do decide to do this on your own, or with some friends that help, or whatever the situation is, the NUMBER ONE RULE is: talk to someone (like inski from evergreen if that is who you are talking about. he is a mechanic there) who knows and make a list. Triple check the list and make sure you have everything, and you will probably still end up missing something anyway. Nothing will ruin your day more than slapping it all back together and realizing that you are missing some small part that you didn't know you needed and now it all has to come back apart.