E7270 motherboard replacement hands on experience

so I followed parts people video instructions to replace two E7270 motherboard.  this model has an improved service design compared to the older E7250/7240.  much easier to take it apart.  no prying of keyboard bezel or touch pad etc.

a few hands on tips:

there is no need to remove speakers when removing motherboard. the video shows this step of speaker removal which is not necessary.

there is no need to detach heatsink and fan assembly if your replacement comes with it installed.  you can simply remove the mobo and heatsink together as one unit.  I actually did remove heatsink for both units, trying to move a motherboard of a working unit but with worn keyboard.touchpad to another unit that does not POST but with good keyboard.touchpad.  

I did find Dell factory used too much thermal paste which are a bit dried up.  it is though easy to clean off the old paste and apply new one.  the screw to fasten the heatsink is more tightly applied than the others, so use strong steady force to avoid stripping the screw.

another tip is to reattach wireless antenna carefully.  I somehow banged one of the wireless antenna socket as well as the wireless card socket for the AUX (black) from a poor mating attempt, so the two would not mate anymore.  this had never occurred to me before that the connectors would be irreversibly damaged.  In the end I used a WWAN antenna for the wireless card.  somehow wireless still works with reasonable internet speed.  but that was a bad experience.