T.P.
My 26m old daughter is in a big girl bed, and we have a door knob cover on her door so she cannot roam around the house at night. This has helped keep her in her room and in bed. When putting her to bed she knows she can get out of bed, but cannot leave her room. After a few nights the novelty of playing in her dresser drawers, pulling all her diapers out etc. got old and she began just going to sleep. I never made a big deal about her making a mess, I Just had her help me clean it up in the morning.
I know it's too late for the nap time question and that I'm going against everyone elses advice, but I have found that if my daughter is over-tired it makes sleeping a BIGGER struggle, not easier. She missed 2 naps over the weekend when staying with her Aunt and at nap yesterday (monday) she slept 3.5 hours (normal nap is 1.5-2 hours) not waking until after 5pm (normal wake up is 3-ish). I also wondered if I should wake her so she would still go to bed at her 8pm bedtime, but decided that she needed the sleep (and I needed the time to clean..lol). I am happy to say she went down for bed at 8:30 without a problem and slept all night. One of the sleep doctors, I forget which one, said "sleep begets sleep" and I really do believe that. This is true only for days when I know she is sleep deprived or has missed a nap the day before though. On a normal day I don't let her sleep past 3:30pm.