I am in the same boat...I am due in 9 days and the boys will be 18 months apart exactly...
We gave our first a new room and kept the nursery the same, i am just changing out the name on the wall (when we decide on one!!). We moved Luke into his "big boy room" about 6 weeks ago because I wanted to give him plenty of time to adjust. I have not made a big deal out of the new baby because I am not too sure how much he can really "get it" until it is here. We talk about it, he knows a baby is in mommy's belly, but really beyond that i don't think he knows what is about to hit.
I did hear to buy a baby doll so he can play with the doll and do stuff like change diapers and hold it gently like we will be doing with the baby....so we will see. My mom just ordered one on amazon for him. I hope to give it to him on Christmas, assuming we don't go early!! I can give you the information on it if you are interested.
DOUBLE STROLLER dilema!!! EVERYONE i talked to HATED their double stroller except the ones with BOBs...We have a Peg infant seat that only fits into a Peg stroller. So we actually bought 2 double strollers. I got the Peg Aria 60/40 for the infant seat to snap into. People with twins did NOT like it, but people without twins did like it. Everyone with a front/back double HATED THEM...too big, heavy, bulky, etc. I haven't even opened the box yet for the Peg, so can't really say much about it, but i am glad i have it because it is so light...
THE BOB: I was Against it because i did not want to be a BOB person...there are plenty of other ones out there cheaper. HOWEVER, it got such rave reviews and I jog a bit, so i needed a jogging double stroller anyway. IT IS REALLY NICE!!! If I had gotten that before the Peg, I would have not bought the Peg at all. (which is another reason why i haven't opened it, i may re-sell it). It is very easy to maneuver and is not terribly bulky and my oldest seems to like it. It is NOT CHEAP!!! HOwever, we got it at REI with a 20% discount and they offer a 100% lifetime warranty with it. I have a friend with twins that hers started tearing a bit by the feet 2 years after she bought it and they replaced the whole stroller free of charge. That was worth it to me to pay the money. There is also a bar you can purchase (i haven't yet, and may not if I keep the other) for 100.00 that you can snap an infant seat into it and the other side is a toddler tray...every one i talked to said it was a must have.
NOW...all that said, I still have no idea!! If you want to send me an email in a month after I have had the kid for a while, I will be happy to pass on any information/opinions from that!
We did keep our oldest in another "convertible crib" and not a toddler bed...I just wanted containment for sanity's sake for a while. He probably would be fine in a toddler bed, but when I was planning on where he would be in 6 months, i had NO IDEA!! I am happy with that decision.
I bought another monitor with only one receiver, figured that oldest wouldn't need more than one and really probably doesn't even need that...only because we have a 2 story and i wanted to attempt to keep an ear on everything!
Seriously my biggest thought is that I will just sling the baby quite a bit and stick with a single stroller for a while too...so, like i said, i can get back with you as to what i actually end up doing!!!
Good luck, I have SEVERAL friends in the same boat and we are all kinda freaking out together....so you aren't alone!