Don't see any reference to this in documentation. Is there an "Uninstall" feature for solution packs?
No, you can't uninstall solution pack automatically.
Solution Pack may put different elements :
1) in the Mega_Std or Mega_Usr of the environment
2) Data in the System DB
3) Data in the Repository
For 1 it's easy to manually remove. For 2 and 3 not easy.