Hey Brian, a man after my own heart.... The quick Fix Download, can't beat it when there is a bit of spare dosh about! Well the good news is Heathrow Pro is a download, it's dead simple, you just download the demo, if you like it, you register it and the demo boxes dissapear! you can get it from here:
http://www.s114327879.websitehome.co.uk/heathrowpro/index.htmAs far as other downloads go.... IMHO, stay away from the PSS Airbuses as they are out of date and flakey unless you want to get in to the realms of merging IFDG/PSS products. You can download the PMDG 737NG which is one of the best serious aircraft addons but is simple enough for a beginner to use comfortably after doing the tutorial flight. To be honest, I would look on Ebay or Amazon to get a boxed copy of the 737-800 which works out cheaper than buying the download of the NG then upgrading to the 800. (The base NG pack is the 600-700 models which are not in our fleet) Addons such as FS Passengers can be a lot of fun and there is a demo available to try before you buy. As far as scenery goes.... Active Sky 6 is a great weather environment and improves the quality of cloud, precipitation and weather in general. Ground Environment Pro is also a great addon for improving the ground scenery quality. Be warned though the vast majority of addons can affect your Frames Per Second rate and can slow your sim down considerably unless you have a beefy machine!