if you have no tolerance, 100mg is way way way too much for most people. erowid, unfortunately (and oddly) does not have good dosage rates, but using heroin and oxycodone (both similar in strength) you should probably be taking about 20mg to start.
as for the high, i dont know if youve done other opiates, but morphine is often considered to be far less recreational than products such as oxycodone, heroin, and hyrdocodone. it will make you sleepy, lazy, and floaty, but will be lacking the euphoria of the other substances. Dont get me wrong, it can still be fun, but its not a super awesome high. Dont rail it for your first time, just eat it. expect to puke, especially if taken on an empty or near empty stomach, but its not like puking after alcohol, its kinda just a purge.
as said above, confirm what you have before taking it. although we cannot do pill ids here, there are plenty of websites where you can search the imprint to find out exactly what it is.