The first step in replacing the struts is to raise the vehicle and open the hood.  Instructions on how to safely raise and support the vehicle can be found in the repair section of the site.  With the vehicle raised and supported you are ready to begin.   Remember to never remove the strut retaining nut until the spring is compressed. 

Start by locating the bolts indicated with red arrows in pictures one and two.  Soak these bolts throughly with a penetrating lube before you begin.  While waiting for the lube to take effect, start gathering your tools.  I also suggest you have a mat or something to sit on as you will be spending a lot of time on the ground.  Once you have gathered your tools start by unhooking the ABS cable from the strut shown below with a blue arrow.  There is no need to unplug it, but you may if you feel the need to free up room.  With the cable unhooked, loosen and remove the two 17mm nuts shown with the red arrows.  At this time do not remove the bolts, only the nuts.  Next using a bottle jack or something similar, raise the control arms until the sway bar end-links are no longer under tension.  In picture five you can see the bolt that holds the sway bar to the strut.  Remove that bolt and let the end-link swing out of the way.  Now remove the two bolts that hold the strut to the knuckle.  With the bolts removes you can now free the strut from the spindle.  Now turn your attention back to the  three bolts that secure the struts top mount.  Usually these are 14mm, but I have seen other sizes used depending on who manufactured them.  Loosen all the bolts 10-15 turns.  Then remove the two nuts furthest from the fender.  Now with a firm grip on the spring/strut assembly remove the last nut.  With the the last nut remove the whole assembly will drop free.  MAKE SURE YOU HAVE A GOOD GRIP.  The entire unit weights over 20 pounds.  If you are not sure have a helper hold the assembly while you remove the bolt. 

You only need to complete the next steps if you are reusing components off the original assembly.  If you have all new parts you can assemble them and skip the next steps.  Next you will need to compress the springs until they are no longer exerting force on the spring seat.  With spring compressors positioned across from each other slowly compress the spring until you can wiggle the spring between the strut and the spring seat.  Once the spring is loose you can remove the locknut and dust cap.  With those removed you will only have the bearing locknut left.  Before removing the bearing lock nut again make sure the spring are loose and not compressed up against the spring seats.  Volvo uses 4-6 special tools for this job.  You can use a set of hex bits and wrenches and do the same thing safely. 

Either using all new parts or the ones you scavenged off the old unit, assemble your new strut and spring according to the instructions the manufacture provided.  The whole thing goes back together in reverse order.  I suggest putting it all back together hand tight and then after checking all the clearances torquing it down.  The three top nuts get 25nm.  The two spindle bolts should be torqued to 65nm plus an additional 90 degrees.  The sway bars get torqued based on the brand.  I generally use about 25-30nm on them.  At this point make sure your ABS cable is plugged in and connected to all the retainers.  Also make sure the end-links are not binding or interfering with the brake lines.  Lastly lower the control arm and the car.  As you lower watch for binding or any clearance issues. 

If you just installed coil overs, I suggest starting with the perches at least one inch from the bottom.  On the first drive pay close attention listening to any noises that might indicate a problem.  This install requires you to preform several operations which can be dangerous.  If you do not feel comfortable, your new suspension professionally installed.  As always.  USE CAUTION.