1) Logan is correct in that it is difficult to determine exactly how mch you will pay, because bids are now hidden. However, in general (see following for the exceptions), all 3 major PPC programs (Google, Yahoo and MSN) use the same formula with regard to how much you pay ... which is exactly one penny more than the person below you has bid. For example if you bid 0.10 and the person above you bid 0.50 and the one above that bid 0.75 (and there are no other bidders), you would pay 0.10, the person above you would pay 0.11 and the person above them would pay 0.51. If you are the sole bidder, you would pay the minimum bid amount (0.10).
With regard to the old Yahoo system, there was a feature of some bid management software called 'competition killer' that adjusts your bid to be one penny below the next-highest bid so that person cannot take advantage of the 'bid gap' while you still do. For example, the person below you bid 0.10, you bid 0.15 and your competition bid 5.00. Rather than let your competition get 0.16 clicks, your software would adjust your bid, setting it at 4.99 (and adjusts it every time your competitor does). That way you still pay 0.11 and your competitor, above you, pays the full 5.00. Sneaky. This is useless, now, since the new Yahoo is now hiding competitive bids, like Google and MSN.
Note that this bid formula (the 'bid gap') does not apply to the top few positions (5 in Google and Yahoo and 3 in MSN), where the positions are decided by the bid amounts alone, and the bidder pays full price. If you set a MaxBid of 50.00 and were the top bidder, you would be in position #1 and you would pay 50.00 per click regardless of what those below you were bidding. Note that these top positions are not affected by CTR in the same way as the rest of the positions are.
2) In my industry, Search-only is the way to go. However many people claim that Content searches bring them a good ROI, so I guess it depends a lot on your industry ... plus a little luck for not getting into too many 'parked' domains.