I have to replace the top lcd of a 3DS XL (also known as 3DS LL) and have problems dislodging the hinge. I've done may 3DS's ...
Only use original batteries. I used 3 different brands, all had problems. I only use original batteries now for iPad.
digi and lcd are not fused.
If you've done well, you'll still have the black adhesive on the frame and the edge of the, you can simply reuse them. Do make sure there are no glass shards stuck to the adhesive on the frame before you stick in the new one.
Basically works similar like the iSesamo opening tool. Work your way around the complete edge until the plastic frame is seperated. Reheat when necessary, typically reheat for every side once, and if there are lots of cracks go slower and reheat more. Once the frame is separated you now have the touch screen with the lcd still attached to it. Reheat the area on the touch screen (!! - do not heat up the lcd directly, it does not take high temps well!) which corresponds with the edges of the lcd, work side by side. Use your knife-like tool to very slowly cut trough the adhesive, and make sure you keep the edge of your knife/tool in line with the edge of the black bezel of the touch screen (to not damage/scratch/
soil the lcd). Work all the way down untill you finish one side. Finish all sides the same way, preferably leaving corners with lots of damage to the touch screen for last, as they tend to be a bit more difficult.
Since you only need to heat op the adhesive you can use a hair dryer rather to heat up in specific places, than heat the whole display assembly in an oven with the risk of damaging plastic parts. Procedure is basically identical to the TF300 of which you can find many disassembly guides online. Heat up outer edges in circular motion to soften adhesive. I use a thin metal blade-like object, normally used either to remove wallpaper or flatten walls after filling holes with filler (don't know the exact name in english).
2. With some wiggling it should be easy to get about half a mm of space between front and back. Once you can fit in your plastic tool, run it along the edges, apply some pressure when necessary and slowly seperate the front with motherboard and everything attached from the back cover. This whole process took me a good 5 minutes and there was no damage to the back cover whatsoever.
3. Follow any tutorial you can find online to disassemble further. Basicly it comes down to disconnecting the cables, removing vibra motor and antennas, removing mobo, removing usb board at the bottom and sister board at the top (watch out with the volume buttons), powerbutton also at the top, and mounting al these in the new display assembly.
4. When front is completely assembled, just click it back in the back cover. Start by sliding in the top, much like an iPhone 5, and apply pressure to fit the rest in. Check the edges. Put sim tray back in. Test. Done.
EDIT: forgot to mention in the beginning: REMOVE SIM TRAY before you start prying!
I don't understand what the fuss is al about with repairing this phone; Just replaced the display module of one and wasn't that difficult at all. I dreaded doing this repair because of ifixit's low repairability score and ordered a new back cover as well, just in case.
All I can say is that the people at ifixit kinda used the wrong approach and most likely did not have the proper tools. I'll explain shortly how to repair this phone:
0. You need a putty knife, as thin as you possibly can get, needs to be nice and bendy. Look at ifixit guides for ipod classic to know what kind of tool I mean. Also, buy the display with frame, not just the lcd+digitizer. Also I suggest to use a wide opening tool, about 4cm wide, they are also much stronger the small ones.
1. Use putty knife between edges of back cover and display. Try to wiggle the putty knife in between the display frame and the back cover. Start at the sides. Watch your new display module to see where there are cables present, so you don't damage these.