If it is time for new struts, fine, but get the heavy duty spring seats (like XC90). You will need new strut nuts, 2 for each side, as they get 'stretched' after initial torque of 52lbs. Make sure you have a good quality spring compressor.
You do not need to remove the caliper, the strut will move to the rear and then come down, out of the way. Just be careful with the ABS sensor line!

Measure what? If you are replacing with Sachs, outline the old strut position with a pencil and try to put the new strut on the old lines. Rule of thumb: get an alignment afterward at a reputable shop, should be around $100.

There is a trick to check for bad spring seats: Get a large wrench or channel lock pliers and try to turn the large nut on top of the strut clockwise. If there is resistance and the nut wants to turn back to its original position, the spring seat is good.

Did you also check the end links? Just turn the passenger wheel to the left, reach behind the wheel grabbing the vertical link and shake it. If it moves, the end link is a gonner and will rattle with bumps. The end links have to come off when removing the strut, might as well replace them, the OEM don't last that long anyway.
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My back feels better when I sit in a Volvo seat