my timing cover is leaking antifreeze (heater is blowing cold and temp gauge is going to hot) what would be the estimate to fix

What is your question?

2000 Ford explorer V-8 engine. Heater was blowing cold about 2 weeks. I took it to my usual mechanic he thought it may be a bubble in the line. told me to fill it wit antifreeze and drive it- revving it to see if that would take care of the bubble. I drove it for almost a week back and forth to work. On Thurs April 7th I noticed the heat gauge was going up to hot. So I went and got more antifreeze and a new radiator top (thinking that that it may have been old) and drove it home. Husband took it out on the highway next day and it was smoking ans antifreeze spilling out. Took it to mechanic 4/10 and he thought it was the water pump. On 4/12 he let me know it was the timing cover that was leaking and he didn't have the tools to fix it.