A clean re-install?

For reasons I am not going to detail (you will find them in separate post in same forum, if curious), I decided to reinstall Windows 8.1 on my FSX PC. Before I actually pull the trigger, I am trying to avoid silly mistakes by asking here about your experiences.

I currently have a standard HD with Windows 8.1 installed on it, and a separate SSD with FSX_Acceleration (with SP2) and a bunch of add-ons:

- ORBX products (Global_base, Global_vector, OpenLC, various FTX_terrains, various FTX airports)

- FSGlobal 2010 mesh

- ASN

- REX4+soft_clouds

- UT2

- Carenado planes

- A2A planes

- EzDok

- IR5_tracker

- FS_Instant_Approach

The main question is: What would be the cleanest way to reinstall all this? 

The second question is: Is there a way I could make this less painful, for example by keeping FSX and Add-ons already installed on SSD and just re-installing Windows on HD?

The final question is: what should I really avoid doing (typical mistakes)?

Many thanks for your help!!