I understand that w/ being a 1st time mommy it's hard to hear your child cry. (not that it's any easier when you have more =]) But it really isn't "cruel" to let your child figure out how to go to sleep by themselves. At some point, they have to. And take my word, it'll be easier now than when she is 2. A good technique... go in after about 10 min, don't pick her up. Just pat her back, soothe her. Leave and wait 15 min. Repeat... don't pick her up. Tack on 5 min each time. Just like she has learned that crying will get you in there, she'll realize you aren't going to come running every time she fusses.
I had to do this w/ my 2nd. She was just a little older than yours and it took about 4 nights of her crying herself to sleep before she got it. That may seem harsh, but it worked. After that 4th night, she went to sleep and we didn't have ANY more trouble w/ her going to bed on her own.
Just keep in mind how much harder it will be if you wait much longer. Trust me... it's A LOT worse when you hear, "Mommy!" along w/ the crying. =]
Hang in there and be strong. Remember, it's not a punishment to begin to teach small steps of independence. You need your rest, too. Not only as a SAHM, but also if you're going to be starting work. You are a great mom!!!
~K.