I just replaced the trunk springs on a car and decided to document the process. Here it is step by step with pictures.
In the top left picture, you can see that three of the springs have broken. This is what causes your trunk lid to not open easily. New springs are available under Jaguar part number BD-19204 from most suppliers. First thing to do is remove the nut off of the small bolt. Then cut or push out of the way the springs so you can remove the bolt. Be careful not to cut yourself as the springs are under tension and have sharp edges. Picture above right is what it will look like. Do realize that this is the left side. The right is the same procedure but mirror imaged.
The next trick is to put the bolt from the inside of the curve facing outward. Stretch the spring using pliers and place the hole over the bolt head. Repeat for 4 more for a total of 5 and you will have what looks like the picture below left.
Now put the nut onto the bolt and no need to tighten. Prize the spring up enough to grab the springs with vise grip pliers. Although not shown in the picture, a pair of their needle nose ones would make it easier. Now renove the nut and work the springs off of the bolt and you will have what looks like the picture on the lower right.
At this point, insert the bolt from the inside out on the coil (Picture below left) and then insert the bolt onto the main base so that you can attach the nut onto the bolt. Do not tighten at this point. You should be at the picture below right.
Before proceeding any further, I would recommend you take the bolt and sleeve off of the arm. The second picture at the top of this article shows it removed. The sleeve is designed to rotate as the trunk opens and closes so needs to be cleaned and lubed to operate smoothly. Install it back into place once done. Now take the trusty vise grips and grip all 5 springs as far away from the bolt as possible. You are going to straighten the springs out enough to go over the bolt. They will have to rotate on the small bolt which is why you did not tighten it. Once in place, tighten the small bolt and you are done. Should look like the picture below. Overall, the total job including removal of the hinges and replacement of springs should take about an hour per side if you don't rush.