Replacing timing chain tomorrow!!

[85 500sel]

Posted last week about getting my timing chain replaced at 125,000 miles. Well, I'm scheduled to get it replaced tomorrow. I wanna take time out to thank you all for your advice. I have to drive 90 miles to get it changed. Hopefully, I will make it there ok. I will post when I get back tomorrow. By the way, what changes can I expect to see in performance etc?. Is this just a preventive maintenance fix?. Will my mpg. increase? If it wasn't for this website I probably would have kept driving this machine without not even knowing the damage I was doing.The previous owner really took great care of this car the last 22 years, but he somehow omitted the timing chain. I went through the service records that he gave me and here is just some of the items that he replaced:
replaced injectors @ 116,00 miles
new water pump @100k,
new michelin tires @ 114,000k
replaced all drive belts @ 100k
R134 conversion @ 106k
new motor mounts@ 100k
Every oil change was documented for the entire 20 plus years. The owner had 4 benzes and a 3 car garage so he sold the "oldest" benz.
Thanks in advance.