I have 737-800/900 installed, I have seen on offer 737-ng in the shops here and am wondering the following questions.the 800-900 install had some option to upgrade the 737-ng but I did not take it as I did not have the software, If I now go buy the software will I be able to install it without overwriting some 800-900 bits ? any other problems with doing the install this way round.also if I buy the 737-ng what exactly will it give me that I do not already have in 737-800-900 ?

If you're flying the -800/-900 package, then you have to have the -600/-700 already installed. I believe the -600/-700 series IS the NG package.If I'm wrong, someone please correct me......

You can buy the -800 add on WITHOUT having the -600. BOXED VERSION ONLY

Not quite what I am geting at, I have already bought the 800 boxed product and installed it, It is a fantastic product, what I want to know is that now I have installed it would going and buying the NG product add anything to what I already have?if it does what is it that would be added ?

I would assume that the "NG" is the 600/700 add on. This was the first aircraft released by PMDG. If you purchase this you will get 2 additional models to fly. As for avionics upgrades, the 800/900 is the upgrade and as such I would recommend a uninstall of the 800/900 prior to the install of the 600/700 then re-install the 800/900 this should bring you to a full up to date 737 NG 600/700/800/900.