My AV '62 RI P-bass is wearing GHS Precision Flats 55-105, fitted/changed from the Fender rounds when new. Any changes to truss rod were minimal from factory settings & I don't remember having to change it since, for about 3 or 4 years.
IMHO - if you want to change strings at all - you're going to have to gain confidence in setting up, it'll pay huge benefits in the long run, getting the action & playability exactly how it suits you - without the bills!
There are hundreds of youtube set up videos, not to mention our very own Basschat Repair & Technical content http://basschat.co.uk/forum/12-repairs-and-technical/
Cheerz, John