M.,
congrats! It's me again, E..
I was 6 years old when my sister was born, until then an only child. I had always wanted a sibling but to tell you the truth, I was rather disappointed when the baby came. (I'm 37 now and still remember all that too well, you can see how hard it was on me.)
Everybody just looked at the baby, baby got all the gifts--even though it didn't care. Then when my sister was getting older--moving around, walking--she got into things and destroyed them (like homework that I had to redo). My mother was always telling me that she is so much younger and that she did not do it on purpose and that I should understand. Well, I didn't! My son's are almost 4 1/2 years apart. I vowed to myself that I will never tell the older to understand. And up till now I think I succeded. I told him that he needed to be careful where he left things laying around because little kids destroy things and that I will help him in any way to protect his things. Bought him an IKEA Billy shelf unit. He keeps his clothes in the bottom with a door on and on the upper shelves his posessions. I told him that it will not be a problem if baby takes out his clothes but that anything important he needed to put on the top shelves. In RI we were in a 3 bedroom with the 2 boys sharing a bedroom for sleeping and our guestroom, Sebastian's desk and my craftroom was the other room. And I told him that this is also our save heaven from baby (who was 1.5 to 2.5 when we lived there). We had all the things in there that were treasures to the two of us, he could let some stuff lay that would have been dangerous to baby because we either had a gate up or the door was closed. I take things away from baby (he is now almost 4) and tell him that it is Sebastian's stuff and he is not to touch it, but I do that with our things sometimes as well. I think I did a pretty good job making sure that my older son was "protected" from baby and I think you really have to view it very often that way rather the other way around. I know babies will have the need for protection but sometimes older kids need more help than baby get already by nature.
Good luck!