Replace all the nuts & bolts with new ones, so much easier to cut stubbern ones off than spending hours with WD40.
Have the new bushes in the new trailing arm before you start, if they come already fitted then you're laughing, if not then I'd go for polybushes unless you have a press or a good vice.
Remove the nut on the chassis end first, then remove the axle bolt and take the trailing arm out by knocking it down and under the axle casing.
Once the arm is out of the way you can remove the triangular chassis bush and renew it.
Reassembly is the reverse of the above. :D