Honestly for something like that I would use a cold solder tool, it uses a battery I believe and can be located online, These are very delicate so heat has to be min! just enough to set the solder. As far as a discharge you can remove battery and touch the two terminals together with like a screwdriver blade or you can use a test light to discharge the capacitors stored power.
If you need further assistance I will be glad to help you.
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I have soldered tons of things both hot and cold, I have never done a cell phone yet however I know how delicate the boards are and I have seen it done, the board disscharge is done as I stated. If you have soldered before then you should not have any problem with that, I do not know what to set the temp to on that though so I will opt out and let another expert try to help you.
Sorry I couldnt help more.