Downloaded this game the other day and already I found Ghost Recon and it's add-ons/mods my new favorite game.
Go through basic training a couple of times to learn the keys and don't change them first off, There's quite a few controls so messing with them complicates things too much.
This game does feel complicated at first but it's my third day and already I learned the keys and have got to lvl 9 of the campaign.
The graphics are ok for such an old game – I'm running it @ 1280×1024 res and it looks good enough imo.
If you get hit by one or two bullets you're probably going to die, So keep an eagle eye out for your enemy – if this means scoping every 2 seconds then so be it, Remember it's a realistic game unlike Team fortress or counter strike.
Keeping your men alive means you get to allocate skill points either for stealth or weps etc which makes your ghosts better at covering your back, Island thunder and desert siege adds quite a few things including new weapons so I recommend getting them, One thing I like is the silenced sniper rifle.
If you haven't played this then do so, It's not all that difficult as some people make it out to be. As for advanced warfighter etc, Well I like this first series more atm, It really does feel like the best of the series.