i think this is how i had my viper before i ramped the cost up:
http://www.edshipyard.com/#/L=60M,7tw7tw7sW7sW3we0mI,2-5K5A5A3m4s5K3c,7fO7Q44yG10i
the shield cell bank is where the real defences are (B has more charges than A), though you do need to activate it before your shields collapse, and it takes quite a while to kick in too. if you time it right though you can stay in the fight for as long as you have charges.
in a resource extraction site you'll probably run out of ammo before you run out of shield cells. the credits are great at RES's, and the combat is less intense. get your friend to fight there for a while as you get used to dogfighting. the credits will be good and you won't be getting ripped to shreds as fast. much better place to learn and earn. then you'll be able to throw the millions into your ship for one of the more expensive fits, or even something like a vulture.
as a playstyle choice i like fixed MC's on my viper (reminds me of BSG). with the tight grouping and good agility the viper can work very well with fixed weapons. the cobra on the other hand at least needs the lower wing mounted weapons gimbled as they are too far apart to hit small ships. for me fixed weapons are more satisfying to fly with, but really the best weapon system to use is the one you work with the best.
while it is true that lasers strip shields the best and projectiles crack hulls the best i find 4 weapons on a target kill faster than just 2. so if you do take a split weapon type approach make sure to gimble one type so you can fire all 4 at the same time. using just 2 weapons at a time will improve your ammo expenditure efficiency, which will improve how long you can stay in the fight, but it will drop your kill speed.
a power plant will not help you fire the guns for longer, only a power distribution unit will help with that. however a power plant might help with overheating problems, i'm not completely sure on that one. it's easy to get all 4 multicannons firing for a long time, you don't even need 4 pips to WEP for that. after being frustrated with the pulse laser in my sidewinder (ran out of juice too fast) i switched to MC's and have had a preference for them ever since. it really is a personal thing though so mess with the different weapons to see which you like the most.