Hard drive error, importing from Time Machine to new drive and misreporting of drive capacity

Hi,

Recently when trying to upgrade to El Capitan my Macbook Pro told me it couldn't do this because there were problems with the hard drive which couldn't be fixed. I took it to the Apple store and they confirmed the drive was failing and replaced my 750 gb drive with a new 1.5 tb one with El Capitan installed. I got my machine back yesterday and as part of the setup process told it to import my backed up data from Time Machine on an external drive. Everything is functioning fine but out of curiosity I went to finder and "get info" on the hard drive and it tells me the capacity is 750 gb, not the 1.5 tb I'm now supposed to have. More alarmingly, again out of curiosity I went to disc utility and in there it says about the hard drive "S.M.A.R.T. status: Failing. I can't imagine how, but my gut instinct is wondering whether importing my data has somehow caused the failure and problem with drive capacity as I'm sure Apple would have checked the drive after installing it. After a little googling I saw something about problems importing Time Machine backups to a drive of different capacity to the old one but I didn't look much and didn't really understand it at first glance. I'll have to go back to the Apple store but I'm just wondering if this rings any bells with anyone. Has anyone ever had these problems or got any ideas what's going on? Could something in my data cause a problem like this? I have Clamxav which isn't flagging any viruses. Does anyone know anything about importing Time Machine backups which were originally on a different size disc? Seems frustrating if it is true this is problematic as surely a lot of the time the use of Time Machine is when switching to a new Mac and a lot of that time the drive capacities would be different. Everything functioing fine at the moment but it's strange about the drive capacity and worrying about the failing status.