Macbook pro dropped, seems like hard drive damaged , few questions about it ?

I have Macbook pro which was dropped real bad. its booting up but seems like its hard drive is gone. Do we have any hard drive test built in macbook pro. I am helping my friend to fix it. He mentioned he made a time capsule backup in an external hard drive. If in any case we need to replace the hard drive is their any way to retrieve the backup from external hard he created. I am trying to retrieve any information from current hard drive. but he is worrying more about if we can make it live again with new hard drive.
Please help

so far i have tried running AHT on my friends macbook pro but i waited for about 10 hrs but it just stuck at the hardware diagnostic screen. I removed the hard drive from macbook pro and tried it in a acer laptop and ran hard drive test. Test showed that hard drive was damaged. Now my friend said he made a time capsule backup on an external seagate hard drive. Now i am planning to try a new hard drive, install OS and then running time capsule recovery from external hard drive. Can i do that ?? or would it be any complication in this procedure ?