What method to use?

Hi,
the first step you should take is to find out where and/or how the program saves number of uses. To find it out you can try filemon and regmon since it is most probable that it is saved in some file or registry. You are right that #4 should be easiest (in most of cases) but be careful - CRC can be hidden somewhere and it can be hard to find.
Also be careful with on thing, assembler used by motorola has some conventions inverse to intel - for example MOV BX,AX moves from AX to BX. Also you mentioned recompiling - that you can't do without sources - you can just patch the code.
To get some ideas, try to look at Krobar's site - here are loads of tutorials that should give you clue what to do.
Regards,
least