You can see that he tried really hard to weld the exploded turret back together, but it just wasn't going to happen. In the end he got the documentation on the alloy and so on, found a foundry in San Jose (or somewhere nearby) that could make that alloy to order, and had them manufacture him a new turret to the original specs. So it's as close to original as you can get without actually being original. Same with the wiring-- he had new cloth-wrapped copper wire made. And the tyres, too. Tour guides were told that he called up the company that made the tyres originally and asked if they still had tools and molds kicking around for WW2-era Panther tanks, and they said they didn't. Then he offered them a massive pile of cash if they could find them, and suddenly they did, and could make him a new set of rubber tyres for his wheels. I don't know if that's true or not, but it does sound like how he tended to go about things.
As far as I know, the Panzer IV is still in limbo. I expect Auctions America may end up eating some of the expenses for attempting to sell a vehicle after the official auction had ended. The 5 high-value vehicles were set with a really high reserve because Collings didn't _really_ want to sell them, but would if they got a big enough offer. They were things that would draw in a high-bidding crowd but could also be the centerpiece of a major tank collection, so they were set super high in the hopes of dissuading even serious bidders. I don't think they quite expected Microsoft millions to show up, or at least for anyone to be willing to drop quite that much cash on anything.
It might be different if there were another Panzer IV anywhere in the US (besides, I think, one rusted-out hulk kicking around somewhere), since then Collings could take the cash and get another one to restore, but I suspect that if there was anything else worth buying around, Paul Allen would already have bought it.
I gotta say, it was surreal to hang out with people cheerfully spending hundreds of thousands or millions of dollars at a time. Some stuff when for super cheap (the AMX 13 was a STEAL), but there were some serious piles of cash moving around there.