Cadillac Repair: Check Coolant Level problem...., coolant level, cadillac seville

Question
Hi Bill I have an issue. I just purchased a used 1994 Cadillac Seville SLS (i think its SLS) in september. The whole time i had it two messages were popping up "Check Coolant Level", and "Service Ride Control".  Occasionally as i was driving the "Service Engine Soon" light will come on.  Well on friday my engine started over heatting and the car would stop.  So I went and got more coolant put in the car and now the overheating has stopped.  Well now as of yesterday the "Check Coolant Level" is starting to appear again after just a few days. The car is running very well  i am not having any physical problems happening yet but these messages are scaring me a little.  My first question is...

1.) I looked under my car several times and noticed no leaks...but why would the coolant level message come back on soo soon?  could the mechanic just not have put enough in?? i noticed he put two bottles (maybe gallons) worth and after each time he filled it with some water.

2.) is what about the service ride control and the Service engine soon?  cars are soo much trouble and i am a poor broke female student lol.. so i am hoping you have a little light to shine my way LOL  thanks for your help :)  

Answer
If you are mechanicaly inclined or know of someone who is, You will need a DIGITAL VOLT/OHM METER, Simple electrical schematics, Test procedures and picture locations of the components within the system that is causing you problems of which can't be done on this website which only allows one picture. I do not have a website so you will have to e-mail: onlineautohelp@msn.com in order to obtain the information necessary to fix your vehicle.