There are two kinds of hard drive users: those who've had a hard drive crash and other who've not had a hard drive crash yet.
At first I'd try to get some file recovery software and try it yourself. It can't hurt and will be less expensive than $2000. I can't recommend any to you because I have a 2nd drive that I back up my first drive to and I also use a cloud service (never know when the house may burn down). Be aware that this is a very slow process so plan on days of your system cranking away and since the drive has crashed, there's no promise of success but I doubt it would make things worse.
To get the high-resolution originals, you'll need to use recovery software or a recovery service. Note that often, if the originals are able to be recovered, the files are recovered but not their file names or folder structure (e.g. you'll get "recovered_0001", "recovered_0002", etc.). It's possible to match them up with the LR catalog, but that will require command-line expertise on your part of that of a friend or colleague. But see if you can get back the originals first.
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Don't you have backups? If so, restoration is simple. If not, then you have learned a very expensive lesson.
Your photos were not stored in the Lightroom Catalog.
You need to have the Catalog file and all the photos to do a complete restore, and these can be on different disks. If so, you lose whatever was on the external HD but not whatever was stored on the internal HD.