Hi johnny999,
I am just a flight simmer as you intend to be.
I am not associated with Laminar Research but offer the following information.
Answer 1. The Steam version of X-Plane is a 3rd party product taking a commercial advantage of the development work carried out by Laminar Research. Laminar has advised in other parts of this forum they will not provide support for this 3rd party product. If you want good support go for the original from Laminar Research.
The boxed set of X-plane 11 is not available as yet. When? Contact Randy at [email protected] to ascertain when it will be available. Randy will give you a quick response. I intend to go for the boxed set when available.
Answer 2. I respectfully suggest you will need a new PC. However, before you rush out a buy a new machine download the demo version of X-plane 11 and try it on your machine. There are some time restrictions in its use and restricts you to one airport in the USA. If you find it does not work have a look at the following at http://www.x-plane.com/kb/x-plane-11-system-requirements/ I also respectfully suggest purchasing a unit with the recommended components. On another website it has strongly been said to stay away from anything AMD as performance will be down.
As you are in the UK have a look at this site http://questions.x-plane.com/9701/advice-x-plane-11 for a new computer. In reading a flight sim magazine produced in the UK I understand this company is well respected for flight sim systems. I also understand they specialise in X-Plane.
If you are tech savvy ( I don't know) you may acquire and upgrade certain components as you go.
If you prefer to do your own work in the upgrade, ascertain if you can get hold of Windows 7 otherwise you should upgrade to Windows 10. If you upgrade your existing machine with Win10 then you have to delete all of your existing software and progressively reload as required. With a new machine you will have no option but to use Win10.
Hope this helps.
Glenn