You can extract an ER tablet and convert it into IR form with most or all of the ER forms of Morphine I know that are available simply by scraping off the coating, crushing it into powder and cooking it up with water into a spoon until you get a clear liquid, then filtering it into an oral syringe, ready to be dosed orally, rectally, nasally, or converted into freebase to be smoked - IV is also possible though you shouldn't be IVing an ER pill (or any pill really) since you won't ever remove all the binders and wax and will be doing a massive amount of damage to your veins, plus we all know the other dangers of using the ROA and its highly addictive qualities.
I haven't plugged Morphine but I've tried oral, nasal, IV and SC(subcutaneous) administration. With these ER pills I'd recommend the procedure I mentioned above and starting with 20mg nasally or plugged and working up from there if necessary, redosing works just fine so it's better to start low and work up than overdo it.
If you'd like to take it ER you may or may not have already broken the extended release at least partially just by crushing it depending on the particular binding mechanism of the pill in question, so I'd still advise starting with a low dose and working up, as 100mg Morphine ER is a big difference from 100mg Morphine IR, regardless of ROA.
It'd help though if you told us your current tolerance to opiates/opioids, then maybe someone could give you a more accurate starting dosage to work from, but my method should work just fine since if you experience quick effects you can be fairly certain you've broken the time release, and that means you'll be able to redose in 15-20 minutes when effects have definitely peaked and you know you aren't at a high enough dosage yet - and if you are, even better and you can save the rest for later.
To dose nasally you should take the liquid through a filter into an oral syringe, tilt your head to the side, and drop 0.1-0.2ml of the liquid into your nose at a time using the syringe, the keep your head tilted for about 30 seconds, and repeat until all of the liquid with your dose in it is administered.
Since the powder could be unevenly distributed in an ER pill, the best thing to do is perform the procedure on the entire 100ml, then put the solution in a container or glass, using a precise amount of water, say 10ml. Now you know each 1ml of liquid should contain 10mg of Morphine, and so 2-3ml would be a good place to start and work up from.
If you wish to take it orally (though this is the most inefficient ROA with Morphine), I'd recommend around 40mg as a starting point if you already have at least a little tolerance and you may end up needing more or even the entire 100mg, but start with the 40mg in solution, wait 20 or so minutes, see if you're feeling it, if not you're probably okay to take the rest as you've likely not broken the time release - if you are, decide if you need to dose more or not to get where you want to be.
If you wish to take it rectally which is probably the most efficient ROA outside of smoking or IVing it (both of which are a bad idea when you're dealing with ER pills, even if you break the time release), take the solution and check out Bluelight's awesome guide to plugging here:
http://www.bluelight.org/vb/threads/247323-Anal-Administration-(Eneme-Plugging)-A-Complete-Guide
Hope this helps
Also if you're not in a hurry, wait for other users to chime in, they may know more about your particular pill formulation and be able to give you better advice than me since I only have experience with MST Continus pills, the EU equivalent of MSContin.
