SGS could not re-gas mine. Some oil had leaked and they would not hold new gass anymore. They sent me new one for £ 88. SGS is a good, friendly and reliable company. The struts are easy to take out and even esear to put them back. The hardest part was to find someone holding the boot open. To undone the lower part of the strut you will need to open the roof and stop in the middle of the opeing to access the lower pin.
But I understand that if you are the proud owner of a lexus you may be willing to spend the double for the original parts which are known to be crappy.