Did mine recently, although all of them apart from the front/rear as the garage did that when they welded a new boot floor in, so I'm talking about the pipes on the swivels and rear axle. The old unions can be very easy to round, so either get a proper brake pipe spanner on them or cut the old pipe off so you can get a proper socket on them. No harm in a bit of WD40 pre soaking here and there but make sure you aim carefully...don't want to spray discs etc!
When I did mine, ironically the T piece on the back axle stripped when I was taking the union off, not screwing it back in. Someone has obviously gone a bit mad at some point. It was annoying as it happened late on and with all the rest of the job done the poxy thing was a showstopper. Assuming you don't need the vehicle, run round early and make sure that everything comes undone before refitting, so you are not stuck without parts at the end of the day. Also have a couple of large sockets or anything cylindrical so you can gently bend the pipe round it.
Probably worth fitting some new extended braided flexis at the same time if you have any intention of lifting the truck at any point, and braided flexis will improve braking performance as they do not swell under pressure. And seeing as you will need to lie in the muck and bleed the system, check the pads too!
Gunson's Eezibleed is quite a good bit of kit...however having just changed all my discs and pads I'm not convinced I've got all the air out (calipers had to come off for a rebuild) so I'm not an expert! I'll try letting them bed in for a bit as advised and see what they are like.
Good luck with it!
