Umm. lets see. In order to get the arms one has to first gain access to the newest place Iwagakure. In order to get the arms it would only make sense that one would have to go to Iwagakure and fight Deidara. Now, fighting Deidara won't be simple, as a matter of fact finding him won't be that simple. At the same frequency that Mando shows up in the stables, will be the same frequency that Deidara shows up in Iwagakure. Once you find him there, you will be able to fight him. Of course it is needless to say that you will need to beat him. However, things can't be too easy because it wouldn't be any fun now would it.
You not only have to defeat Deidara, but you must survive his final attack on you, Jibaku Bunshin, Suicide Bomb. If and it's a big IF you are able to survive his Jibaku Bunshin, you will find his scattered limbs. It will once again be needless to say, that you will not be in the best of shape after barely surviving his Jibaku Bushin. You will of course need to see Sakura (Pray that you don't get attacked while traveling) and get healed, but you will also need Sakura, a great medical shinobi, to sew on your new arms. Now healing you is a normal task for medical ninjas, however; sewing on arms is a completely different task so you will have to pay and pay dearly.
Do you remember the cost of the operation in Hoshi Gakure (Yes, that operation)?