As for removing one ...
1) you need a good hot iron that can sink heat (but NOT a solder gun! NEVER a solder gun!). $29 electronics stores hobby irons need not apply. Needs to be a good professional unit.
2) flow a little solder on each side to "wet" the joint and get good heat flow.
3) moving from side to side, heat until all solder is molten then GENTLY rock the cap to pull the leg slightly through the PCB. If there is any resistance, STOP and reflow. Switch to other side. Repeat until cap is removed.