I have another quick and simple DIY for those that love to tinker with their car. I've notice that my rear hatch was lifting slower than usual and would sometimes only open up partially. So it was time for a replacement.
1. - Get a 2nd person or find something to prop up the liftgate since one strut is not enough support for the heavy liftgate. (I had to hold it up with my left arm and with the right fit the new one on

)
2. - remove the existing C clip spring retainer from both ends of the strut. Use a small flat head screwdriver to wedge it out.
3. - Now here comes the tricky part. Depending on which strut failed or how it is being supported (parked on a level ground); you need to wiggle the strut out. For me the right side was sagging and I had to lift the hatch all the to the top with my free hand and rock it a little and the strut just pops right off.
4. - For the new strut prep it by opening the retainer clip but DO NOT pop them out completely.
5. - I inserted the end attached to the frame first and locked in the retainer clip and then do the same for the end attached to the hatch. Remember the orientation of the original strut and do the same for the other side. That's it.
I now hear the pressurized swish sound everytime its lifted, like it should on a new car.

It took me about 20 mins for this DIY, good luck and have fun tinkering.
Part number:
51247294199 = Gas pressurized spring, trunk lid (x2)
2007 non auto liftgate part number.