Sugar is going to be the hardest for me to give up, I like my sweets.
Is Splenda a good substiute or just replacing a bad thing with another bad thing?
It's replacing a bad thing with another bad thing. Read up on sweeteners!
It will only take about a month before you will prefer things without sugar, and that preference may last a lifetime (if you don't allow your addictions to get in the way).
Many moons ago I went on a WW diet (at the time I only wanted to lose 20 lbs and the diet was very strict, not like today's WW menu). It killed me to not have sugar on cereal, and in my coffee/tea, and to give up my beloved pepsi!
By the time I was finished (2 months later), I could no longer stand sugar on those things, and I couldn't stand drinking Pepsi as it was so syrupy sweet! It was really weird though because for MANY years afterward I still craved Pepsi (or at least my memory of what it used to taste like), but yet I couldn't drink it. It sucked having an unfulfillable craving.