Also keep in mind you can only buy Wii point cards in 2000 point value only which are $29.95, although on the Wii Shop channel you can buy in 1000, 3000 and 5000 values with a credit card (works out to be $15 per 1000 points)
NES games are 500 points, N64 games are 1000 points and the rest are either 600 or 800 points, so your money will go fast
As far as download times go, well that really varies on your connection, plus for me it seems to take a while to get a game using the Nintendo Wi-fi USB adaptor, as far as N64 games go for me, its about 20mins a game (albeit i am on a 256k connection =/)