My old thermostat has 8 wires and I'm trying to figure out how to install a Honeywell Rth2310b thermostat.

The terminals on the old stat should be basically the same as on the new stat...with a couple exceptions anyway. Note the color of wire on each terminal before removing them and reconnect to the new stat on the same terminals. 8 wires typically indicate a heat pump, so in the configuration menu you'll have to tell it whether to energize the O terminal in cool or not. If you have individual wires on Rc and Rh terminals, you must remove the factory jumper between those two terminals on the new stat. If not, you'll burn out one of the two control transformers or possibly damage your new stat.

In the configuration menu, you'll have to tell it whether its a gas furnace or electric furnace, select the way the fan operates and possibly limit the cycles per hour on both heat and cool modes. There's a lot of subtle entries that need to be done to 'tailor' the new stat to your likings also.

I think it would be best to rely on someone thats a bit familiar with HVAC to change out your stat for you..... as once it is changed, all possible functions of the stat need to be verified as correct in operation.