i have a fulltone fulldrive mosfet and it doesnt have enough sustain for my taste. My question is, is a sustain/compresser pedal worth getting or is it going too be like my fulldrive?
You'd be better off saving the money, selling your amp and getting a valve amp.

No point in sustaining for longer if you sound crap.

And yes, I used to have an MG30.
It's the difference between eating a single Belgian chocolate profiterole, or drinking two litres of brake fluid.