My van is blowing white/blueish smoke from the tailpipe. What could be wrong?

I believe white/blue smoke is caused by the vehicle running rich. Basically the gas-to-air mix is wrong. Too much gas.

sounds like either a headgasket problem or oilburning from scored pistons. watch the coolant level if it drops you have head gasket leakage, if the coolant stays up and you need to add oil all the time, then perhaps the rings and or valve guides are to blame.

Other than what you think is "white/blueish" smoke from the tailpipe what is the sympton of the van? A blown headgsaket would be white smoke with a sweet smell in the exhaust.

Most likely you have a head gasket issue! My recommendation is to take it to a shop request a compression test, this will most likely be the least expensive option before throwing a lot of different parts and not fixing anything!