One thing that is VERY important, consistency. When my daughter was born, my mom stayed with me a good month. She taught me, pretty much the same time every night, or close to that,
Get the child ready for bed the same time every night. Start with a bath. You call the shots, not the child, getting a child ready for bed, should not take hours and hours. So many parents feel guilty for not spending enough time with their child, over indulging only does more damage. Kids need boundaries, limits. Do yourself and him a favor, stick to a schedule.
A bath relaxes the child, eventually you should put the child in his/her own room. You will be creating dependency if you allow the child to stay in your room. Don't do that. They need to learn to fall asleep in their own bed, their own room. Creates a healthy happy normal child.
Trying to get him to sleep, go in, reassure him, but only for a short amount of time, you can't stay and cuddle and cuddle. Go in after 20 minutes, then 30. Its almost rewarding his behavior, by allowing him to do whatever he wants. You will have to hear him cry, eventually he will fall asleep.
You must stop this behavior before the new one arrives. Again, consistency is key. Be firm, loving, reassure, then put him back down, he won't like it, too bad, he needs to learn this is bed time, and to go to sleep. You can do it.

Good luck, keep us posted.