I just went through the same thing with my sled. Blew up the engine and didn't know where to go or what to do. I replaced the whole engine myself for like $2500 after plugs/misc parts/coolant etc. If you replaced your engine for $2500 and then sold it for $7500-$8000 next fall you'd net $5000-$5500 to upgrade. I don't think you could part your sled out for more than like $3000-$3500 honestly. And it's a long slow process to get the whole sled parted out and sold either locally or on eBay because people will only buy the higher fail/ware stock items first ie... suspension, track, body panels, bumpers, etc. A good running used engine would be the biggest ticket item and unfortunately you've probably only got a good core/bottom end.
I think Beartooth is right you could probably offload the sled as is as a project for realistically like $4000 to put towards your upgrade if you went that route.
If it's just a top end you would probably be looking at like $1000-$1250 all in assuming you do the work yourself. Then if you sell for say $7000(because a rebuilt top end probably won't pull as much as a full rebuilt motor with a warranty); you'd net $5750-$6000 towards your upgrade.
So to summarize.
Rebuild engine for $2500 and sell for $7500 = net $5000
Rebuild top end for $1250 and sell for $7000 = net $5750
Sell as is = net $4000
Part out = net $3000-3500, maybe, after a lot of work, and assuming every piece sells.
Really depends on how much work you want to do/are capable of doing yourself.
Where are you located?
https://www.idahomotorcyclespecialties.com/ Give these dudes a call, they were super helpful and got me a full rebuild for like $2200 after I gave them back my core.