Hi Pam,
Welcome to the hobby of fish keeping and to aquaria central! Looks like you're a pretty busy mom... So from what I understand from reading your post you have a 10 gallon, got a few fish and know you are left with one gourmis.... Until your water perametres(amonia, nitrate, ect. levels) settle down consistantly to healthy levels and you've learned a bit more I'd keep it down to that one existing fish. From reading the other replies, you've gotten to know about gravel cleaners and stuff like test kits... It is a good idea to for now do between 20-30% water change(eith gravel vacume) every few days, after when your tank gets settled down a 30% water change once per week is good. As well as every time you do a water change test your water for ammonia, ect.
Later on when you are ready for more fish, rember that generally the rule of thumb is: 1 inch of slim bodied fish per one gallon, and compatable species with in your comuntiy. Check out the species/compatibility section on this site. I kbnow you dont want to be reading a whole lot of stuff but some of it unfortunately cant be avoided so one good site with not too much moumbo jumbo is:
www.thekrib.com
here you'll want to look up the begianers faq.
Also one good book wich you can read bits at a time and that I personally dont find too overwhelming is: "Aquariums for Dummies".
I know all this most be overwhelming for you as it was for me, but it does get easier as you go along. Also I agree on what you said about there should be warnings on aquarium kists...well maybe not literally, but the staff at the lfs's should educate peaple on proper care/maintence with fish keeping as well as fish species, ect. Some just dont seem to bother and only care about getting a sale, which frustrates me big time!!!
Anyways, good luck,
mt_marcy!