His suit is probably made out of common materials--hell, we could perhaps make one today (though it might be a bit bulkier). I figured he was more damaged than what he appeared to be on RotS, so the only vital function his suit serves is to breathe for him...though he was doing that just fine moments before the droids placed the helmet on him. Perhaps the helmet has some sort of visual augmentation in case the fire injured Vader's eyes.
^ yeah thats probably right, though is it possible that the Emperor put something into the suit so that if Vader ever betrayed him the Emperor could just blow him up. Or if the emperor died, then something (poison) would be injected into vader
That would explain why Vader said "I must obey my master" even though in the sith betrayals go on all the time. It would also explain why Vader said that he wanted to look on luke with his own eyes and then when luke said he would die and vader said it was too late, he knew this because of the poison. It also makes sense because in RotS he had no problems breathing after being burned to a crisp