Sure we can help you bethany !
You've got a 45 gallon tall. We'll need the exact LxWxH dimensions of this tank.
Measure under your stand and post back these dimensions too.
LxWxH in inches, and any doors you have also.
Do you have a brace in the middle ?
Be as detailed as you can - a pic would be good too, but not necessary. Selecting the sump can sometimes get tricky - but only when you try and pick one that is too big for your available space.
You said you don't want to drill the tank - so you'll need an external overflow. These can be bought online.
You'll need a return pump - again online normally best price.
You'll need either some pvc pipe, fittings, hoses, tubing and hose clamps.
Some sort of spraybar or pvc fitting arrangment to connect the return line to the top edge of the tank ( shoot the water back in to the 45 tall )
How handy are you with plumbing stuff ? Have you ever worked with pvc, pvc glue and this sort of thing ?
Tell us what you plan to do or are doing with this tank.
FO, FOWLR or REEF
What do you have in the tank now ?
How many powerheads ?
Do you like powerheads, or would you like to get rid of some ?
Lastly - do you want to do a refugium too ?
If not now - you think maybe later ?
After knowing these things - we can get started.