thanks would be much appreciated

Dumbug I'll make a sound comparison this evening or tomorrow. For me it makes a huge difference.

Thanks Oliver. Would you suggest a voltage divider to bring it down to Line level?

in that case i shall leave gameboy as is for now thanks for the replies

I strongly recommend a decoupling capacitor. Mono's output on pin 31 is biased to 1/2 VCC (2.5V) so that there would be continuous current (unless there is a decoupling capacitor elsewhere in the signal path).
The +/- 2.5V voltage range exceeds standard line levels, e.g. the signal is very loud.

DMG already has relatively clean sound, noise floor is low and has a nice shape (white, slightly low-pass filtered stereo noise). For the other models (pocket, color) with their thin sound, hum and hiss noise, such a mod would make sense, but on DMG I think it's not worth the hassle.

tbh im not technically inclined with the GB internals i read up some where there was a simple mod taking pin 31 and ground of the cartridge connector and soldering it to a mono output jack giving a clearer output was looking to do just that as im not a soldering genius so apologies for my noob ass question/replies

What steps in this mod are you hoping to take? Are you just adding a wire between the VIN pin and an RCA jack? Even though the audio isn't going thru the CPU, it is still going to have the same ground floor and DC offset associated with the VIN pin.
I think what you want to do is cut the VIN pin at the cart connector and solder a wire to an AC coupling capacitor, then to your RCA jack. There should be some improvement since he audio doesn't go thu the CPU and the noisy amp IC, but it will probably be subtle at best.

looking to do the direct audio out mod to my DMG and wondering if theres any sound comparisons out there before i butcher my gameboy also can it be done with a RCA type jack?