Your first isn't quite old enough to benefit from a lot of preparation. Though there are a few picture books about welcoming a new baby which we enjoyed. What worked for us and close friends (4 pair) who had kids with this spacing was having the baby give the older child a gift at the hospital - something fun to play with. You'll appreciate this, too, when you need a bit of rest as the parent of 2 small kids. Another trick is to constantly reassure your older son that his new baby loves him, is infatuated with him, is watching him, is interested in him... Everyone loves flattery, and this helps the older child feel like he isn't being replaced. We gave my older son tasks that made him feel helpful - like fetching a diaper or burp cloth, or entertaining the baby while we changed her. These made him feel so proud, and helped reassure him that he wasn't being replaced.
Regarding your more focused question - the crib - you might want to get a pack n play or something of that nature for the younger baby as if your older son is not ready to move out of the current crib, you won't enjoy the process of putting him in a toddler bed. 2 months before a baby is arriving is not the time to interrupt your night time rituals. (We're the only family of the 4 I know with the same spacing that had the older child in a big guy bed before the second came along, and we made the transition at 10 mos when my older son was climbing out of his crib.) The majority of our neighbors (10 kids in total) kept their kids in cribs until 2.9 - 3 yrs. So, if you can afford it, and your older son is not a climber, you might find an alternative solution for the crib move for now. If you want to move to a toddler bed, for my son, it meant that one of us had to sleep with him or lay with him to get him to stay in bed. With my daughter - the type of kid who wanted to be left alone - we're just accepting of the fact that she's roaming around their room until she wants to go to sleep unless we want to struggle and keep putting her back in bed. Sheets, fancy night lights, ticket systems, etc. haven't really been effective.
Congratulations and best of luck.