HD needs repairing but optical drive NOT reading discs.

Question

My problem is this: I have a June 2010 21.5" iMac which is out of warranty.   Disk utility says my HD needs repairing.  No problem, I have the original install DVD.   Trouble is my DVD drive has suddenly stopped reading discs! I rand Apple tech support for help and I asked them if I could simply buy a usb external DVD drive and re-install that way? Since I will also have to reinstall from DVD; Logic and Pro-Tools.   He said no!   Consequently I'm booked in for repair next week at an Apple store.
Is that a way of Apple making money and I CAN actually repair the HD via an external usb hard drive??  Did he convince me to take it to an Apple store so they gain cash from me that way?
Do I take it in for repair?  The Apple Tech Support guy gave me no clue as to how much this is going to cost.
Or don't take for repair and buy an external usb DVD drive?
I struggle with computers at the best of times!
Any help greatly appreciated.

Answer 1

I've used ancient Compaq "Multi-bay" external drives and a variety of other random-vendor external USB drives with Apple laptops and Apple servers, and they've worked.  In several cases, I was using the old Compaq drives because the integrated DVD drivers were dusty or had failed — DVD drives of all sorts can and do fail, Apple, third-party and otherwise — and the Compaq drives were handy.  That Compaq Multi-bay drive booted an Apple Xserve Intel box with a bad slot-loader, too. 
If one drive fails, debugging suggests trying a different drive.
If you don't want to be concerned about compatibility, order one of those (not cheap) Apple external DVD drives.  I now have a couple of those around, and they work.
It's quite true that newer Apple laptops don't have DVD drives, though most of these systems offer a recovery partition on the disk, the ability to create external recovery partitions on the device of your choice, newer ones have Internet-based recovery if you're lacking a drive (booting from Apple's servers via the Internet), and the Mac boxes I've tried will boot from various random USB devices including the old other-vendor DVD drives, and from the Apple external DVD drives.  With another Mac with a compatible wiring connection (Thunderbolt and cable on newer Mac systems, and FireWire and cable with a pair of older Mac systems), Target Disk Mode (TDM) can be used.  The installations can also be copied to other hard disks, and it's also possible to network-boot most any Mac system, if you have a server around.  And there's also the remote disk installations that some Mac systems can offer.   Put another way, there are various and good alternatives to device-integrated DVD drives.
DVD is an old and mechanical technology, and it's variously a flaky one.  Given a choice, I'd rather boot OS X off an external hard disk or solid state or flash device or via TDM, just because it's faster and more compact.  This because I'd rather not carry around the weight and volume of that DVD drive all the time, on the off chance I might sometime eventually need to recover.  But an external random DVD device does work, too.
As was mentioned else-thread, there is no special chip required in the drives.  Given the command set and status-level differences from drive to drive I've seen and given the failure rates I've witnessed with DVD and CD drives from all vendors including Apple, I wouldn't expect every drive to work, but I've seen nothing that Apple does here that would prevents a random drive from working.  And I've used random drives...