So I recently got a pretty nice used 07 500 with 174k miles on it for a good price. I did a little research before hand but didn't see all the stuff about transmission problems until after I bought it. Long story short I'm kinda nervous of it. I have a few things.

1. How noticeable should the downshifts on this car be?
- When mine downshifts it's not hard but it's definitely noticeable.

2. My fluid isn't brown or black but it's getting there. I've read several horror stories about these cars having bad transmission problems after changing the fluid. Should I go ahead and service it? If so: Full flush? Drain and re-fill?

I'm just kinda worried now, paranoia I guess, shifts are good though... not too hard and no slipping. Seems to lag a little between 1st and 2nd though... I read this is common though... right?

It's a nice car and I like it a lot but I really don't want to have to replace the transmission, any tips to keep it going good?

 

It's the Aisin 6 Speed by the way!!