First of all: I only work with one system that has a raid setup, so I can only share my experiences with that system.
Raid solutions quickly become a stinkin' pile of c... when a disk fails when it is just set to striping (yeay...speed, boo...writing same data twice). Unless there is a contingency drive (preferably same brand, type and size) put in the raid setup, you likely will have a big problem trying to get your raid setup to rebuild itself.
I work here with a Linux server that has a software raid with 4 disks and a separate boot drive. Till now it was every time still able to rebuild itself after a calamity. But only because one of the 4 drives is there as a contingency. Now I always get confused with the numbering, but if I remember correctly this setup is called: raid 6. the number might not be correct, but it is a compromise between raid 5 and 10. Can't be bothered to look it up, sorry.
However, I never recommend a raid setup to anyone. Although the speed difference is noticeable, it isn't that much. It also doesn't weigh against the problems you run into when one of the standard consumer components breaks. It could take sometimes one or more days before the raid was usable again.
If there would still be an option to have the broken drive work long enough to clone it, you should be able to use the cloned drive to continue with the raid rebuilding. Turn the broken drive upside down and see if that helps (you would be amazed), There is also the trick of putting it in a zip-lock bag, make very sure there is no air inside the bag with the drive and putting it in the freezer for several hours. If you have no means of doing that, don't bother with this trick...which is a 'hail Mary' at best.
And when you do connect the drive again for cloning, work as efficient/fast as you can to get all data off it. Prepare beforehand everything you need so you waste as little time as possible. If the heat doesn't kill the drive, the condensation most likely will. In the mean time it is best to not use the system with the RAID at all. Avoiding too many discrepancies between drives and all that.
If it contains 10 years worth of data, where are the (confirmed) backups? Raid is not backup!!!!!!!!! Anyone who thinks it is...should seriously be punished by 10 whiplashes... so they will never ever forget that! Ok, that may be harsh nowadays...wearing a fool's hat at home, work and their commute for 10 days then.