First time posting. I've got a 1987 aw11 with a 4age from an ae82.
I bought a suitable trd lsd online with the intention of putting it in myself, but having a look in the owners manual and reading a little online it looks like a complicated and expensive operation.
Just looking for more info really, anyone have any experience?
what would it involve? is it complicated?
how much would it cost to get it fit? what are my options?
 

You can actually have the diff out of the gearbox in about 15-20mins and only need 1 socket / wrench and a hammer to do it. (Assuming you have the gearbox out of the car and on the ground with no auxilaries).
 
Start by undoing the bell housing bolts, there are around 20 of these on the perimeter and a couple inside the bell housing near the input shaft and clutch fork (use your socket / wrench for this). Then on the diff and bell housing there are some over lapping surface points that you can tap with the hammer to begin separating the two halves. You'll get it separated till you get them about 1.5" apart and it will get a little tight, this is because the reverse gear shifter fork will be trying to come off at an angle and needs a little bit of a wriggle to get it to come off. After that, you lift bell housing off and you can see the diff, which you just lift out of the casing.
 
If it's not clear, I might take some photos / make a video this weekend on doing it.

I've got an idea of what your talking about but if you're willing to take some photos or a video that would help heaps. I've got a service manual which should help aswell.
Removing the transaxle, can it be done backyard styles with a couple jacks and jack stands? Ill have a look under the car tomorrow.
You've made the benchwork sound much less difficult than I imagined. :)
 

I use an engine crane to lower the motor and gearbox onto the driveway (on top of some MDF), then put a rope across the two points and lift the back end of the car up with the crane. I have seen others do this with jacks and stands, but it's a little more time consuming.

Then wriggle the motor across the ground (slide the MDF with it makes it easier!) out into the open so you can work.
 
Working on the box in the car or just removing the box is a royal pain in the ass from my experience, so I recommend the drop motor/box method ;-)

 if you just got a LSD centre, then you will need to press fit 2 new side bearings and reshim their pre-loads by trial assembly of the cases.  the book shows you how to do this, but make sure the old silicone is fully removes from the mating faces before you start. expect that part to take at least 1 hour and you will need a selection of shims
the speedo gear off you current diff may fit, depending on what brand the LSD is.

Page 431/432 of the BGB shows about the pre-loading process that Terry commented on.

Right this is some serious work. Thanks for the pics. I see how drop motor/box method would be the way to go backyard style. This seems far more than I can handle at this stage.
Have any idea what getting a qualified mechanic to do the job might cost?
Will I lose much in the way of street driveability?

It's probably going to be a 5-6hr job depending on how good your mechanic is, so depending on his rates, it could be $500+.
Is your TRD LSD a Helical or a Clutch pack diff? If it's helical, you shouldn't find any lose in street driveability, but a clutch pack based one might clunk and chatter a bit (especially in car parks). YMMV.

its a cone type clutch pack lsd.
will there be increased wear on any other parts? somebody i was speaking with said i would snap driveshafts?

No, you won't be snapping any driveshafts. Unless you have crazy amounts power and super sticky tyres and even then......