I would start keeping track of his sleep patterns in a sleep log. Use graph paper or excel to mark down his wake and down times, etc. You need to know how much sleep he is getting in 24 hours. If it's around 14 hours total, then he may be down to 1 nap very early. I've heard of 10 and 11 month olds down to 1 nap. It took my son a bit longer. He's 15 months and can mostly do 1 nap, every so often he does 2 naps.
Have you checked out Marc Weissbluth's "Healthy Sleep Habits, Happy Child?" I'd check it out from the library. It has some useful information about a healthy sleep cycle for children at different stages in life. When the morning nap usually starts, etc. If the morning nap starts too late in the day, they won't be sufficiently tired for a second nap, but they might be too tired by bedtime.
As for putting a baby down at night, check out some of the other lengthy threads. A lot of moms have asked this recently.