Your preban rifles are worth a few more bucks, and rebuild kits are readily available. I see used ones for sale all the time.
It would seem that the assault rifle bans had three major impacts.
1. It drove Timothy McVeigh over the edge and led to the deaths of 168 federal workers in Oklahoma City.
2. It galvanized the membership of NRA and other groups swelling their membership to over six million.
3. It caused the Impeached Traitor Rapist to lose the Congress and Senate.
BTW the ten year expiration date was a calculated political ploy to stick a Republican President and Congress with a sticky election year issue. If Dubya and the Congress extend the ban they will lose votes, that is certain. How many votes they lose is up for grabs. Weak Republicans will lose their jobs as a result, and this one litmus test issue could change the balance of power; Democraps planned it that way.