I would recommend the CCNA to anyone who works in systems or network administration. I had 10 years of system administration experience when I started studying for the CCNA, including a lot of Cisco experience. I was amazed at how much I DIDN'T know.
I used the CCNA study guide by Todd Lammle and would highly recommend it. It was the only study source that I used, so I don't know the quality of the other ones.
I would also recommend putting together a "lab" of equipment. You can get many older pieces of cisco equipment on ebay, though I'd steer clear of pre-packaged ones as they tend to be overpriced. Do a little research, you only need a couple of routers and switches to really be able to experiment with the different technologies you'll need hands-on experience with for the test.
Having the networking experience and the CCNA did actually help a bit with getting my new job. I have 13 years of experience in systems, networks, and security so I don't know what entry-level wages would be, but if you truly understand the knowledge required for the CCNA, practice in your lab, and don't just study "to the test", then you'll stand out against other candidates.
CISSP, CISM, CISA, CCNA Security, OSCP, CEH