LEXUS LS OVERHEATING AND RADIATOR REPLACEMENT

[ALVIN1993]

I just bought a used 2007 Lexus LS460 with 205,000 miles. At first, i had to jump start it at anytime before i can start it. I thought it was the alternator so i decided to take it to the Toyota dealership on August 30 since the nearest Lexus dealership is about 60 miles from me. It drove fine the first day i drove it. But i parked it for about 9 days. On August 30, I jumpstarted the battery and I was able to start it. suddenly, the engine light came on. I did not know what was wrong so i decided to drive it to the dealership. On my way, the car overheated and steam started coming out of it. So i parked it and had it towed to the dealership. They called me about 5 hours later and told me my radiator was bad and the battery was weak but it could go for a while after it is charged. A quote of $1500  which included some tire repair, brake light switch lamp, and oil change in addition to the radiator was slapped to my face. I called a local mechanic that i usually patronize but he gave me a quote of 300$ which I found it hard to believe since the dealership quoted $964 for the radiator. I was just scared to take it to my local mechanic. Anyways, i gave them the go ahead to work on it but my conscience is beating me to that decision. I feel like i should have had it towed to a different mechanic which could be less. Has anyone replace a radiator on a 2007 Lexus and paid that much ? Did i make the right decision by letting them do it instead of a roadside mechanic?