The front right brake pipe is the nastiest one to change, you'll be glad to hear..
During assembly it's fitted to the car before the engine and gearbox are fitted... so without removing those, you won't have an easy time of it unless you happen to have received a well-trained capuchin monkey for Christmas
The pipe drops down from the ABS unit.. runs all the way along the bulkhead, secured by clips.. and then follows the wheel-arch round until it pops out, near the suspension strut.
The easiest way to attack it might be from below. If you can get the car into the air (on axle stands) it might help.
First disconnect the pipe at each end... just to get the fluid out and out of the way. You don't need that dribbling all over the place...
Find the end of the pipe at the ABS unit and run your hand along it until the first clip. Some of the clips are simple "push-fit" and others are like "hand-cuffs".. you have to open the clip up and take the pipe out of an inner "bush" that has holes in it for multiple pipes.
Work your way along, unclipping the pipe until it is no longer held in place by anything. Memorise which clips are where and what type they are.
When you have the whole thing loose.. it should rattle back and forth a bit.. but not that much because it's an L-shape and crammed in against a lot of tight parts.
You can remove it by dropping it down as far as it will go and then pulling it out from the wheel arch end. It sounds easy but it's fiddly since the pipe will snag.
Your pipe is "old".. so you can bend it a little (to straighten any problem kinks) or even hack it off to take it out in pieces.. but I'd persevere with pulling it.. de-snagging it and generally teasing it out, so that you can use the old one as a template for the new one.
New pipe.. I managed to get a brand new AR pipe into my 155.. but not without bending it carefully in places to straighten it.. to make it easier to slide in. If you are using copper pipe then this will be easier. Obviously the copper pipe doesn't have to be the identical same shape as the OE one.. but it makes sense to use the original clips etc.
Form the new pipe to keep it well clear of the bottom of the inner wing when fitted, otherwise it will fret and wear through. Feed it in from the wheel arch.. grab it on the other side and force it round where it hasd to go... but without kinking it... until the end comes out near the ABS unit. I'd straighten that last "U-shaped" part a little until you get the end out so that it doesn't snag along the way.
So... it's just fiddly and you need to take your time.. but copper will last as long as the car, so it'll never need doing again..
When you attach the unions to the brake hose, put some silicone sealant around the pipe and the thread, so that the union doesn't rust to the pipe or to the hose. The "problem" with copper pipes is that the unions become the weakest link... if they rust then you'd need to cut them off if the hose ever needs to be separated.. which knackers the point of having non-corroding brake lines. You can get brass unions.. they're rather dear.. but in theory will never corrode.