I just got my maxima back after having it not functioning for over a month.

After a month of driving a Ford Escort '95 my car feels GREAT...

They told me they recommended a transmission flush since the fluid was dark brown! I checked it while it was working and it seemed fine to me, would sitting for a month cause this? They told me that wasn't possible.

So... $130 for a transmission flush seems a bit steep for me, and I'm assuming theres no satisfactory way of doing it yourself. Damn.

PS: I also REALLY need to get my bent frame fixed, the front left tire is down to 10% tread after only a few months. The mechanic told me that if I went to Fixit I could get it adjusted and have insurance cover it (past deductable). If I didn't report the initial accident would this be a problem and would it be wise to use insurance instead of paying it myself? (Keep in mind I'm a 19 year old male in California)