cleaning e36 plastic fuel tank help?

[dave v. in nc]

Any experience out there with cleaning out a sitting-for-eight years e36 gas tank?....assume its got the usual gooey crud, but ignorant on what to use to not damage the tank, but to clean it out thoroughly...Considering the $150 purchase of the car, a vert, that needs lots of love...(a used tank that probably is in the same condition as this one, costs more than that on ebay, trying to learn a little something...thanks