I'm assuming it is an early one as the fork leg bottoms are the clear lacquer type rather than the silver painted legs on the newer models.
The Headers (Down pipes) can be replaced at a reasonable cost as mentioned in an earlier reply, also as mentioned the eight manifold nuts can be real heart breakers, but, it is not impossible to do it as long as you are patient and use common sense, spray them liberally with a good release agent, 'Plus Gas Formula A Fast Release' is a good option. WD40 is no use for this what-so-ever, it is a silicon lube and moisture displacing fluid, its a penetrating fluid release agent you want.
Give all eight of them a good blast of the stuff morning and night preferably when the engine is warm (Not RED Hot) for a week before you try to undo them. also a good move is to give them a sharp tap using a drift (6 inch long bolt) and a hammer before you try to undo them, maybe the night before and give them another good drenching of release agent.
Go steady with the hammer and drift they only need a sharp tap, go too silly and you might mushroom the top of the stud stopping the nut from coming right off or bending the stud.
If the nuts feel really tight you can try apply some heat with a gas blow lamp with a fine flame and or try very gently to tighten the nut a bit and then rocking the nut undone and up again if you feel any movement, use caution.
If a stud or studs do break it is not the end of the world, but it is a pain in the arse, they can be removed with the engine still in place but it is not easy.
I had two break on my FZS when I replaced the headers because of pin holes in the collector, and like Sharpie, my pipes did not look anything like yours.
A bit of maintenance:
What I do is to remove one nut from each of the four header pipes every 6 months or so and Copper Slip them and tighten them back on then remove the other four nuts and do the same, careful tightening them don't over do it, the other thing I have done with my studs is to put a 10mm capped stainless steel nut on top of the standard type manifold pinch nut this acts as a lock nut and stops the manifold pinch nuts coming loose or off. This will take about 45 minutes to do and save so many many tears in the long run.
Oh! and the capped nuts look great to, If I ever buy a new bike I will do this Copper Slip treatment from the off.