I have a 96 blazer 4 door 4wd. I replaced the fuel tank,filler neck,fuel lines from the fuel pump to the fuel filter an put a new vent valve that goes on top of the tank at the front. It's started leaking at the front of the tank around the vent valve so i tried turning it tighter but ended up snapping it got a new vent valve an put it on but it is still leaking around it. Am I just not turning it into place right or something. I'm tired of laying on the ground an frustrated lol. Any help will be appreciated thanks

 

Another question is should there be any fuel going through the vent valve in to the line that's connected to it going back to the charcoal canister

 

Hi 96, there should be no fuel in the EVAP system under normal operation. Vapors yes, outright fuel; no. Over-filling the tank and/or parking on a steep downhill incline can, of course, cause this issue due to the design/shape of the tank.
That said; first make sure that you have the correct vent valve and o-ring (I think there are more than 1 type used according to the exact year and model (4 or 2wd, number doors, etc). And yes, these valves can be a bit difficult to get at with the tank installed. Just make sure to thoroughly clean and then lightly oil the o-ring, valve, and tank area and then carefully seat the valve fully into place before you lock it down. A small hand held mirror can help with doing so.