Bob,
The A+ certification is like a hardware install/ os install maint. type gig. Let your department know that they either need to hire someone to maintain the network with the proper credentials, or they need to put you through all thr proper training. You A+ is a good bet because it will stay with you and you can always make some spare coin fixing up folks pc's etc. Fair warning fixing peoples pc's is like a bad marriage, when everything is good it GREAT but when stuff hits the fan its a major SPLAT.
If you'll be the only admin you may want to look into some type of security training. Thats what I do for work the security portion feel free to give me a call and if I can help you out or point you in the right direction I will.