No one can possibly tell you for sure. Far too many variables with the shroom you have, with yourself, and with your set and setting.
NEVER believe any "answer" or advice you get here or elsewhere as "truth." It will surely be just one random opinion among many that disagree with it, all of which are no more than 10% likely to actually apply to you and your situation.
Best advice I think is to look them up at erowid.org, read their FAQ, read lots of posted trip reports under "Experiences" link, follow links to other sites, etc. Read, study, do your own homework, make your own decisions and judgements based on that.
You might also check in at a forum called The Shroomery, where they specialize in shrooms and probably have threads designed to assist first timers like yourself.
Best way to take them IMO is... hopefully it is dried, right?... grind it up to a fine powder in a coffee bean grinder (10-15 dollars at discount stores if you or friend does not already have one). Mix the powder bit by bit with some juice in an empty vitamin bottle or something small... shake real well, swollow, repeat till gone. Powdering helps improve absorption and avoids stomach ache that trying to chew it up can sometimes cause.
Well, good luck and have fun... do it somewhere very safe, and away from distractions and noise... being around people who are not tripping can be distressing and confusing... alone in your room listening to music with closed eyes is usually perfect, and can even give a decent trip on a low dose because you are focusing on the effects and blocking distracting influences out... spacey music or classic psychedelic rock is best for me... but whatever you find suits you best at the time.
Here's a good-luck graphic... they used to show this sometimes on a big screen at Grateful Dead shows... it is spelling out "Namaste" in Sanskrit letters!
(
http://en.wikipedia.org/wiki/Namaste)