The only one I know of is in the SST painting and modelling book (if you can still find one, perhaps someone can scan the relevant parts for you) which was duplicated in the hardback rulebook (can't remember if it's also in the softback).
If it's any help, I build mine like this:
1: Fit the body and legs together then attach the small front and back armour plates.
2: Attach the arms and weapon. Make sure you pick a matched set (should be next to each other on the sprue). I find it best to use gel superglue as you get time to adjust them before it sets. I found it useful to test-fit the arms with blu-tac to get the pose right first. It's best to fit the right arm (holding the rifle) first as it's easier to trim or fill the other one if required.
3: Attach the head and then the shoulder pads, and finally the pack.
Finally, use PVA glue to attach the transparent visor. Superglue tends to melt it. I used a nail with a blob of blu-tac on the end to manouvre it into position.
