Power supply connections are quite simple, all connectors are keyed to only fit in one way, if it doesn't fit, it's not supposed to go there.
In terms of things you have to reconnect there will be:
1 20+4 pin connector on the motherboard.
1 4 or 8 pin CPU connector also on the motherboard.
A SATA power connector for each hard drive and your DVD drive if you have one.
1 6 pin PCI-E connector for your new graphics card.
The only thing you have to worry about is it is possible to force an 8 pin ( or 6+2 pin) PCI-E connector into the 8 pin CPU slot on the motherboard, do not under any circumstances do that, use the 8 pin or 4+4 pin connector labeled CPU. The connectors on the new power supply should hopefully be labeled which should help if there is any confusion.