I'm not sure this is the right forum for this, you may want to post in the Buy/Sell/Trade
But as for questions 1 & 2 I'd suggest either buying ot trading them in the Buy/Sell/Trade forum or going on BrickLink.
I bought several parts from bricklink about a year ago to build up my collection and had very little problems with it. Some orders would take a month to get to me and I had one issue with a seller who never sent me the part, but that ways over like $2 so not that big a deal.
Over all I had 1 issue out of like 15+ deals. So BrickLink can be pretty reliable.