Hi, the fact sp3 has caused some people problems also highlights why it's suggested to slipstream it into a new install disk, there are far less issues that way, so I definitely suggest this is the way to go, because lets face it, worst case and you have problems you can install again, but I have yet to see a system have problems with sp3 personally, but yes there are many that have, but slipstreaming it into a new install disk is a much better approach than adding it after your installed, but without it you will have security holes and be at more risk.
As to drivers there are a couple of ways to go, if it's a store bought system you could go to the makers site and download the drivers for the OS, the next method is to identify each individual component in the system, then go to each of those makers sites and get the respective drivers from them, a useful program to aid this is
Everest, expand the system summary and it lists all the parts, some parts have highlighted text, click on that to uncover a link to go to the drivers page of that item, then use the info in the summary to identify the exact driver you require, repeat this for each part and your good to go.
Now you can back up the drivers from the system, and you can add them to the slipstreamed disk, and nLite does allow the addition of drivers during the process, but I prefer not to do this, I always go for the latest drivers each time I install, I never use system disks because often they are very dated, so there is no replacement for going and getting the latest drivers each time you need them IMHO.
Also no point in backing up the system as it currently stands, not in the main part that is, obviously any files you want to keep will need to be backed up, but the system as a whole would be a waste of time as it wont be the same system\OS again.
Once you have the system fully up and running, and your happy all is well, then thats a good time to create back up's and rescue disks, but TBH I have yet to achieve this, at least where it's worked, I have tried many times, but the people I do it for always find a way to break them lol, so yes there are various ways to cover yourself when your ready, but I'd have to get someone more experienced with this to guide you there, will be interested in doing battle with that demon myself rofl.