It's been a few years since I replaced the guides on the M115 but I seem to recall you need to split the chain to replace the top guide. The pins are simple slide pins and can easily be removed using a bolt and slide hammer although I've heard many people removed them using a stack of over sized washers instead of a slide hammer.
To access the lower rail pin you need to pull the dampener I believe. It's easiest to pull the radiator for access.
Why are you replacing the rails? If you don't have chain stretch there's no need.
If you're bored and looking for something to do then c'mon over to my place and you can help me sand down my 250C for paint prep. Maybe give alabasi a ring and help him with one of his 50 projects.
