Need some Mechanic advice?

i just had a friend tow a older mercedes to a new mechanic who works with foreign cars. It needed a head gasket so when i took the car to meet him and drop it off he told me he would work for 70 a hour. Later that day he contacted me after running some kind of gas test to verify it needed the gasket. He had told me parts and laborer i would be looking for around a thousand dollars. I had decided to go ahead with that and asked about how many days it would take and he told me about 2-3 days. it was Tuesday i had dropped off the car. i called thursday to find out what the deal was and when i should pick it up he then told me that he had shipped the head into have test to make sure it was not cracked or damaged. After reading online that the text usually take about a day i decided to have my wife call friday when i was working and he had told my wife he had got the head and everything was fine and the car would be ready by monday. Today i called to find out when i should have a friend take me up to get my car and i was told that they were waiting for a new piece? the piece is a timing chain guide. i kinda got upset and told the women the mechanic told my wife my car would be ready to be picked up monday and all the pieces where ready just had to put the gasket and head back together. he said that usually takes anywhere from 5-9 hours. I dont know whats up with the timing chain guide but i never was asked to have that replaced also could he have damaged it while working on the head gasket and needs to be replaced and is going to expect me to pay for it? i dont know this mechanic i was referred by someone and read alot of online review from local on yahoo that says good things. i just dont understand why it would take him as long as it is then to all of a sudden say it needs this new piece or does this piece get replaced along with the valves and the gasket he told me that the head gasket kit comes with? also i know my wife called to talk to the mechanic after i did cause i was loosing my cool but she lost hers to cause they did not give any information or tell us how much longer this is going to take. my wife said if the car was not ready by tomorrow we would have it towed to someone else cause of the time and all this hassle. I could have paid a little more for someone who specializes in Merecedes. he does charge more but at least i would have my car running by now. should i be worried that he might do something to my car to hurt it after i drive it so i need to replace something else? i know it sounds stupid but i need some mechanics input on what to think and do. thanks