DON'T DO IT!!!! lol j/k It's easy and at the same time can be a nightmare. It all depends on how you go about it. There are alot of articles on this sit about swapping to TPI that are very helpful. Pre Planning is the key!!!
I picked up a 89 RS Roller project that was originally a TBI and I am in the process of dropping in a 350 TPI motor in
See Here (Back in a Third Gen)
If you do a TPI swap make sure that ALL the parts you need come from the same donor car i.e. The TPI setup, computer, chip, harness. One of the pains is that you'll have to swap the fuel pump to a high pressure/high volume pump. TBI pumps put out about 10psi and the TPI needs 35-40psi. Plan on half a day to a day doing this...pump is in the tank. If your going to upgrade exhaust this is the time to do it because you can just cut the old off out of the way and not worry about it.
You also have to switch little things like throttle cable and stuff.
If you have the time, a warm place to work on it over winter,all the tools with a little bit of patience added in, then its not as bad as you think to do the swap. If you get all the parts in advance and have time it shouldn't take more than a few days or a week to get done.