Need advice on how to take out my stem.

[elmore leonard]

Good Luck with that. I had a old 80's road bike where the stem had coroded so bad, due to dissimilar metals, nothing would remove it. What nfmisso said is good advice but you may have to throw the wood away and hit it as hard as you can with a ball-peen hammer once you screw the bolt back in. Leave the handle bars and front wheel on to give your self some weight and some thing to turn the stem with if you need to pry it loose.