Thanks, interesting read. After that, I think I'm still on the 'it's not necessary' side of the fence, although I can see how you could do it with a wheel truing stand and some stick-on weight things.
Sorry to sound a bit thick here but what do you mean by "out of balance"? Do you mean the wheel wobbles as it turns, i.e. out of true, or do you mean balanced as in what you do to a car wheel when you fit a new tyre (which doesn't usually apply to bicycle wheels AFAIK).
There is an an alternative which did to my bike to turn it into a 1 x 10 by replacing the shifters with a pair of standard brake levers and a right hand bar end gear lever. I later changed it back but worked ok and wasn't too expensive.
It's possible to repair a bb by welding a steel liner into the shell and cutting a new thread into it. I had this done to one of my frames by Argos in Bristol.
Otherwise, you can use a threadless bb but not with modern external bearing type chainsets.
At your budget, I think you're better off buying secondhand. Any new bikes at this price will be so poor quality, won't last long and you won't enjoy it.
Best not to get too worked up about these things. The vast majority of eBayers I have dealt with, both as buyer and seller have been absolutely no problem. There are always a few idiots.
Sounds like this buyer had unrealistic expectations of shipping times. Even in the UK, I give it 7 days from when the item is marked as dispatched before I make enquiries.
Ummm x 2. Wee issue with the front forks. Hope you didn't ride it like that.
PS This isn't the classified forum.