Congratulations! My to oldest are 23 months apart, and my oldest was (and is) a high maintenance kiddo :) There weren't any issues, he was excited about his brother's arrival, because we all were. He loved to help, bring me diapers, wipes, etc. I never required him to, he quickly hopped up and helped out on his own. So let him help as much as he is inclined, but I wouldn't force it on him. He was included in everything, so he felt a part of Collin's care, not forced out for any reason. I did nurse (have with all 4 of my kids), and that was one of the best times to spend with my oldest. Whenever I was nursing, Collin was happy and quiet, so Jerod and I could read, play cars, do puzzles, enjoy cuddling because it was a time I had to sit and relax with both of them. Not to mention that I didn't have to spend any extra time preparing and cleaning bottles!! And nursing allows you the luxury of calming a fussy baby at the breast, so there was less "noise" in the house, making a calmer environment.
Just relax about the relationship between your "babies" and he will feel the joy of a younger sibling instead of the stress, making the adjustment easier for him. Include him and love him just as you have been! Do not leave them unattended together - you'll need to get a feel as to how he is around the baby. Even though he wouldn't mean to hurt the baby, little guys don't always know their own strength, and how fragile babies are. Taking the baby in the bathroom with you in a car seat or bouncy seat for showers, etc. will help there. My oldest are now 11 and 9 - I promise you will do fine! Take care!