How to pull the trim/tilt screw out

[Gradywhite3535]

I noticed the seal or dust seal to my trim piston is failing. I’m going to replace the seal but what tool can I use to unscrew the cap screw that has the four holes on top?can anyone recommend the tool or process of unscrewing/ replacing seals?. I don’t want to mess that bad boy up

 

[Gradywhite3535]

Also how would I go about emptying the resolve to see if there is water in it? Its a 2003 Yamaha 130. I unscrewed the resivor a little and fluid was topped off but I don’t know how to empty it to check and see if any water got in? Thanks