No Problem,
Tools wise the more the better lol, If you dont have a air nailer i would sugest useing screws instead of nails to hand nail on 1x2 will be a pain trust me. Just predrill all the holes just a little under the size of the screw and that will elliminate any chance of spliting. here is a list:
Skill saw (for cutting the plywood)
Cut off saw (if you have one for cutting the 1x2 or just use the jigsaw)
Elctric drill
Adrill bit just smaller then the screws you want to use
A bar of soap (Seriously you smell no JK, If you put a little soap on the screws as you put them in they will go in easier also reduceing your chance of spliting, use it just near the tip so you dont have to worrie about getting any extra in your fish tank.
Some smaller 1" to 1 1/4 screws for the frame
A hammer
and some small brad nailes to attach the plywood to the frame.
if you want to use some glue make sure it will not be water suluble after it sets, gorilla gule would work good dont use a lot since it will foam a bit as it setsup.
Some wood filler and sand paper for the outside to fill in the holes that the brad nails make so that it will look finished.
And then what ever kinda finish you want.
I think thats about all for tools you should need. As for cutting a straight line this actualy can be really hard i know lol. there is a few ways to go about fixing it. Use a guide something that you can handle that wolnt be flexible, could be a 2x4 or i believe thy still sell them at home depot or lowes but a long aluminum guide. if you are aveing real problems use a guide and clamp it down some how c clamps or a screw or two. If you are going to paint it screws wolnt hurt anything just a extra hole that you will have to fill in and sand down. as i have done more and more wood work i have found that drawing a line can reallly help also. But there is always one more way=) if you have a router and a fluch cutting bit you can cheat with thatbut if your jsut starting i would recomend useing finding one of the aluminum saw guides they shouldnt cost too much but they are always handy for jsut about anything. If you dose just use a 2x4 make sure you find one that is really straight or else it willl do you no good any how.
I have to run for now, ill see if i cant get you some basic plans / cut lengths to help you out a bit more latter tonight.