Re: Which bushes first?
The squeeking is mostly from the springpan arm bushes. These bushes take the highest loads and tend to deteriorate first. On the older TS cars these were a solid bush, on later cars (perhaps JTS on) they have the rose-jointed variety (all V6 cars have these as well). The solid bushes are not so bad to remove but the rose jointed ones are much more difficult. Also when removing any bushes you need to ensure that all the material is removed, and you're left with a clean smooth inner surface to fit the new powerflex bushes.
If you do the springpan bushes first (powerflex codes PFR1-713 and 714) then you should also consider the transverse arms as well (PFR1-710, 711, 712), these are easier to replace and also dramatically improve the handling as well.
Last on the list should be the upper wishbones (PFR1-716), they don't do a great deal really, and take the least strain of the lot. I have done mine, but really you can place these last.