I've heard that taking a class for the A+ certification can cost as much as a class in college, keep that in mind as you decide. As an alternative, getting the certification can be as simple as buying and reading a book that discusses it and then taking the tests. You must pass the CompTIA 220-801 and 220-802 with an 80% to obtain the certification. To take the exams you must schedule an appointment with a testing center, luckily CompTIA partners with Pearson VUE for their testing scheduling. Visit there website here: http://www.pearsonvue.com/comptia/ , and create an account. Here you can find the exams you want to schedule, pay for them (It should cost ~$400 for both exams), and find a test center. You can take them together, or on separate days.
Also keep in mind that many colleges and employers will help you get a certification. If your school can obtain a discount on a exam voucher (You can use these as an alternative to paying for the exam via Pearson) take advantage of that opportunity. If you work in an IT position at your job, ask your supervisor if your company will help pay for the exams.
One last note. The hardest part of getting this certification is the commitment. If you take a class, this is easy, if you don't take a class, this can get hard as you may loose interest or be distracted a lot.
I haven't heard of an age requirement and as for the Cisco certification, I don't know about the exams for those. Pearson VUE will tell you, you just need to search for it.