installing osx after hard drive replacement

The flashing question mark doesn't necessarily mean that the hard drive is physically damaged; it just means that the computer can't see a valid, bootable operating system on that drive. This can be a minor problem; you may be able to repair it without taking the machine apart and replacing the drive, which is a pretty big job.

If you've already installed OSX 10.7/10.8/10.9, you have an invisible, bootable Recovery Partition that has a copy of Disk Utility and a set of install/restore tools that allow you to reinstall OSX and/or restore from a Time Machine backup. The recovery partition may still work; try powering up the machine with the OPTION key held down. If your recovery partition is readable, it should appear as an icon on the desktop. Once you've booted from the recovery partition, launch Disk Utility and see if you can repair your main partition. Then try to reboot, and see if the computer boots normally. If it does, that means it recognizes the OS again.

If you still can't boot from the installed OS, you can boot into the recovery partition again, and reinstall the operating system as long as you have a network connection (a new installer downloads from the App Store). That will reinstall the OS/system apps without modifying your user data. Alternately, you can restore from a Time Machine backup, if you have a recent backup accessible; that will eliminate any user data created/modified since the last backup.