rebuild raid five config

If I buy a nas which has raid five config. If the nas failed but not the hard disk?

Will this happen? Is nas more durable than hard disk. If one nas failed and I buy the same brand nas, could the raid 5 be rebuild and able to keep all data easily?

if u are using synology, it can be replace another unit and do the DSAssistant to restore the raid
http://forum.synology.com/cht/viewtopic.php?f=6&t=5656