Oldsmobile/Buick Repair: question : 99 buick century, auto repair shop, buick century

Question
I need help for my 99 buick century V6 ,auto (190,000km ).  It was running great before . and I reaaly like it !
One and half  month ago, after starting , the temperature  went high very quickly (maybe after 10 mins ) , I added the coolant , but , it was leaking .
I brought the car to auto-repair shop , checking result is "coolant intake gasket leaking .(estimate $700 for repair ). I took it back,wanted to shop around , and fix it later  . I didn't touch the car anymore until  last week , BUT when the car be  started , engine was running , but the body can't take it , the car not move . I don't know why ,and I recalled , it was happened before , sometimes , after the car be short stoped (such as stop sign , red light , waiting for right turn ), but it was not move when you gas it , but re-gas it , it was ok . I  checked for transmission in dealer for this case before , and be told it was no error code.  so I didn't do anything for it ,even some friends told me , maybe I need to re-fill some  transmission  oil.

Now ,Could you give me some help about why it not move, so I can have an idea about if  the car worth for fixing .   
Thank you so much

Answer
Hello Ella,
For sure check the transmission fluid level, and bring it up to the correct level, with the correct fluid.
You might find someone who will change that gasket for less than 700, but if they are trustworthy, that isn't a terrible price to ask for that work.

Van