Shifting problem question.
 

I have an 01 monte ss with 215,000 miles.
I havent had the car long but trying to fix some issues with it.
One of the issues is shifting hard into first when it is warm. I know this is a common problem but heres my question.
I dont know if its ever had a transmission flush or anything. The trans fluid looks a little thin to me.. ive used lucas in the trans and it seemed to help out the cause a little but still shifting hard. Would it be safe to do a transmission flush and replace filter with this many miles on it? Or should i try another cleaner?

Thanks for any help.

Fluid and filter change can't hurt but it may not fix the problem.