ISTA is pretty easy to install once you have a good download. Bimmergeeks has a good download and I hear protocols is pretty good too. Easy to install. In regards to tuning, you certain can get decent power upgrade. Some 335d folks are running dual cp3 pumps and I hear getting some serious HP and gobs of torque. Sellers suggest dual pumps can get 1000+ HP, although I haven't seen dual pumps on the x5 yet. For transmission tuning, you can certainly DIY and is very easy as well. Look at xhp, you can purchase their tunes, or create your own within certain parameters. There's also DWR, but I personally run Supthins transmission tune and had been great.