How will big brother adjust?

I'm a full time stay at home mom. I attend classes online or at night a few times a week. I've had my entire summer off and I'm waiting to hear back from a few colleges to see if I can complete a bachelor's program. Conrad does not attend preschool or daycare. I'm nervous he isn't going to adjust well to having a little brother. We talk about it all the time. He pats my belly and talks to "his baby" and it's so adorable. He helps me around the house all the time and for the most part he listens and takes direction well when it's needed. I hope the trend continues and he'll be willing to help me when I need something for his little brother.

 I know he enjoys his time with me and I hope I can figure out how to balance everything. My husband will be able to take 12 weeks off to be home with us and have his own bonding time. We are so thankful. I think it will really help. My concerns are after he goes back to work full time and I'll be doing this on my own half the day. Don't get me wrong, I'm very excited. I'm just also very anxious.

 Depending on finances, we may enroll Conrad into pre-school next Fall, or we may be able to enroll him directly into kindergarten. I need to look into it. I have a lot on my plate trying to figure out where my life is going to be in the next 2 years. I'm going to try to finish my bachelor's degree before Conrad is in the 1st grade. It's my goal. I'm really hoping I get accepted into an online program and the financial aid is enough to help us out. I want to be home as much as possible with our kids.

 For those of you with more than one child, how did your oldest adapt from being the only child to the older sibling? Any tips or advice you can provide? Thanks!