I have an old Raleigh Capri, 12 speed
I've been doing fair amount of cycling lately (~120 miles/week)
My biggest problem is shifting and I would like to upgrade it with index shifters.
I read about the frame so I know it is not worth spending a lot on this steel frame (for the record, it is very stiff and not very comfortable) but I cannot afford buying a new bike so a relatively cheaper upgrade would be fine for the moment.
The six-cog cassette on the back reads "SR6" and the rear dérailleur reads "Shimano SIS". I am assuming the dérailleur is compatible with index shifting. Is that the case? Is the cassette also compatible? What other components should I buy? How much do I need to spend? More importantly, is it worth the effort?