First, you are not running out of gears. 48-11 is a higher gear than was available stock on ANY bike before the 1990's, and is enough to pedal at 35-40mph. Nobody but highly trained racers can maintain that speed, and even then certainly not on a hybrid. Pedaling downhill one would use it for less than a minute at a time unless you're doing a descent in the Rockies. If you run that combo at lower speeds you are going slower and wearing your bike faster than if you were in lower gears.

Second, going from 48 to 52 is only an 8% increase. You're spending a lot of money for a small and questionable benefit.

Third. you are also increasing your lower and middle ranges, which means you lose your lower climbing gears and some of the gears on the middle ring will be higher speed only.

Fourth, to determine if a new crankset will work on your old BB just compare the chainline to your current crankset, which you can find with a Google search or on the manufacturer's website. The Shimano cranks may not work as a replacement for your original crankset, which is probably Sugino.

Finally, please take another stab at being a little clearer about your problem - "i'm down to rear of 6 and have of 7 gears. in 6 with the front shifter all 7spd combos are used and half of 7 are used," makes no sense to me, and the rest of the post is not much clearer.

Thank you in advance for putting a little more time and effort into posting your request for help.