py272

I am new to this forum and need assistance in fixing an old Specialized rock hopper mountain bicycle. I found this bicycle and wanted to replace the pedals. I easily removed the left pedal from the crank arm but the right pedal was very difficult. After trying Liquid Wrench on the threads, pounding on the wrench with a hammer, and then attaching a pipe to the wrench for more leverage, I finally got the pedal off but some of the threads were stripped. With the stripped threads, I was able to thread on (with some significant effort) another pedal. I am pretty certain the pedal will not work its way loose, however, I feel that if I ever remove this pedal the threads would be so stripped that I would not be able to screw on another one. Therefore, I was wondering if it is possible to repair stripped pedal threads? Would retapping the threads work? Someone mentioned installing a helicoil (not sure if this is the right spelling) might be an option. If I have to replace the crank arm, would all Shimano crank arms be compatiable with the existing bottom bracket (the current crank arm is Shimano Exage and the bottom bracket axle is the older 4 sided tapered axle type). Would crank arms of other brands fit?

Thanks for your help