2005 s40 Transmission questions

[SfortyJ]

So I purchased a 2005 s40 t5 with 140k km on the clock for 7k about 2 months ago , a purchase I'm starting to regret. apon purchasing the vechicle I could not find the transmision dip stick , oil and all other fluids looked nice and fresh though so I decided to take it for a test drive. On a test drive to me the transmission seemed fine, responsive, instantly goes into gear from park to what ever gear you select R,N,D ext.
Ok problem 1 , when first starting the car and driving it when I reach about 10-15km there is a sorta grinding metal sound not sure how to describe it at first I thought it was when switching from first to second after using the geartronic it does it in first or second doesnt matter the gear it just does it at that speed and the faster you accelerate the less noticeable it is, last 1-3 sec. Heres the thing it only does it once when you first start the car then after that its gone, the car can be hot or cold as well if you turn the ignition off then on it will do it again, but after it already does it that one time stopping putting the vehicle into park then into drive it will not do it again.

Problem 2, When going light or hard on the gas the car seems to shift fine, when going saying a medium throttle though it almost seems theres a shift flare or slip.

Problem 3, On the highway with a light throttle the rpm's will sometime fluctuate 50-100rpm causeing it to speed up a touch then slow down a touch almost like boost is cutting in and out.

Problem 4, After finally locating the tranny fluid dipstick , I pulled the dipstick and almost had a heart attack when seeing the color of the fluid , its a dark brown and has a few tiny tiny , tiny metal particles in it , but does not smell burnt, to me anyway.

So now my nerves are pretty much shot , I purchased some 3309 atf fluid yesterday I as just gonna drain the pan and refill and maybe do this 3-4 times over the next couple of weeks as I here sometimes flushing all the fluid out on a tranny with dark fluid can cause problems. my question is , is there a plug on the transmission that I can drain it from and is it save to mix mobil1 JWS 3309 with the volvo fluid thats in there and is a good idea to even change the fluid at this point?

Thanks