Senna
I'd go with the sealing and make sure the canopy is sealed too.
I would not pay for winglets for that ship.
If you need more go
Look for a ASW 20 or -27 or LS3 with a functioning ballast system
Enjoy your ship for what its worth today
And as Hank said don't try to fly too fast, do less climbing instead, that's some great advice right there.