Yeah, there really shouldn't be anything special to do. Just make sure both RM and Optifine are the most recent version and you should be good to go.
With regards to the crash: *insert rant about new launcher here* Seems like the new launcher no longer shows the crash report when Minecraft crashes, you'll probably have to go get it yourself. Have a look inside the "logs" folder in your .minecraft folder. There should be some logs with relevant info (fml-client-latest.log most of the time). Post those to some pastebin site, so we can have a look at them.