Hello Bike Forum members.

I am new here 37 years old and from NL Europe. I came out on this forum because I searched on the internet for this Cannondale. Below is mine. Its been out since 2004 and I received in via my family. I made it a mission to take care of this bike for the rest of its life.

Currently, it has the following setup

Ultegra 6500 2x 9-speed groupset 53/39
Ultegra Wh6800 wheelset

The bottom bracket is Shimano Octalink.

Lately I have 2 issues with the bike. The crank starts to get worn and the right shifter is shifting very difficult. I guess its the end of this groupset. My question is about this.
what do I need to change this bottom bracket? I think its BSA English thread. I am planning on installing a Shimano 67/6800 or Sram force/ red groupset of 10 speed. Can you give me an advice on what I need to switch this crank I am quite handy its just a lot of different sorts out there? what type should be the best option for me?

Thank you so much I am not allowed to post pics will update when I am