I'm not familiar with samsungs keyboard, but I'm fairly confident that there would be no built in option to do this. However, android being the customisable OS that it is, there are loads of different keyboards out there you can try to find the best suit for you. That may be something you want to consider.
The two keyboards I use most are
this one, which is the vanilla android keyboard + some tweaks, and
Swype.
The vanilla one looks a lot like the SGS2's keyboard from what I've seen, but has the option to hide the settings/period/comma/voice keys, as well as to turn double tapping space into a period. It is a paid app, unfortunately (there's a free version which is fine, but it doesn't include the option to remove icons or use double space).
Swype on the other hand is not your standard keyboard; you place your finger on the first letter of a word and then drag it over the second letter of a word and so on until you finish the word and let go. At the end of each traced word it inserts a space, so this also would solve your problem.
But like I said, there are loads of different keyboards. Playing around with several is the way to go
