I think you misunderstood what they were telling you. Your engine is not destroyed. If it is a valve clearance issue, a simple adjustment will fix it. That's a normal maintenance item.
Personally I'd be surprised if that resolves the issue.
Still, it might be that the previous owner didn't take the bike for a clearances checkup, and that incremental discrepancies between, what those clearances should be and what they are, brought to a sudden appearance of vibrations that weren't felt before... I dunno, just guessing.
Wow , I suppose it didn't go so well.....unfortunately. I was going to suggest checking engine mounts , air filter ( heavy dust storms etc ) and use Seafoam or similar ( depending on which country OP is in ). Hope we find out what the issue was.
I'm sorry for not giving any updates to this issue.
I have suspected that valves need calibrating (sorry, not sure of the way it's called), or whatever, but they did the distance checks and said it was fine.
They did however say that engine mounts were a little loose and that they tightened them.
Afterwards, I felt basically no difference, although I have completely lost all confidence in my sensory abilities... however, after a month or two of riding, I think I've had a feeling of bike operating significantly better, although that may be me just getting used to it (hence the lack of trust in my own sense of difference in the engine's operation).
Whatever the case may be, the bike is fine, and I do think it's running smoother.
TL;DR - Engine bearing tightening.