For now, just take him into bed with you and cuddle him till he's deeply asleep (you probably will be, too, by then :)
As for tomorrow night, and nap-times, in general, help him sleep in whatever way works best. Then, keep doing what you're doing, even though it looks like he's fallen asleep. Keep at it for maybe another 10-15 minutes. That helps him to really get into deep sleep, and helps him to relax so that he will stay asleep when you gently lay him down. If he starts to wake up when you do any of the letting go or walking away, just swiftly but gently return to your earlier soothing techniques, and he will be learning by this that you will be there if he needs you. Again, just soothe him till he's out. Because somewhere in his brain he knows you will return if he wakes and cries, he will feel safer about drifting off. This is the key point. It might take you a few days or a week or so, but if you follow these basics, you will be laying the groundwork for some really good sleep for Gavin and you for the long run.
After a while, once he really gets the whole sleep thing, you won't need to do this extra stuff.
That's the basic thing. For additional tips, details, etc., get No-Cry Sleep Solution by Elizabeth Pantley (at the library or amazon.com, or Borders - just get it! It WILL help, enormously!) or Nighttime Parenting by Dr. Sears.
But don't make him cry. It will only make it worse - he will find sleep to be even more stressful. Which will make putting him to bed, and keeping him asleep, even harder!
L.