Hop on Facebook and join the group RTAG Nation. If you are prior military, you might not have to pay a dime. If you aren't, the information is still extremely useful. Sounds like you might already know the training path required from 14 CFR 61. Your helicopter time definitely counts toward your certificates - you only have to do the things where part 61 specifies "in an airplane." If you have no intention of going the CFI route to get your requisite 250 airplane PIC for the ATP, note that once you get your instrument-airplane rating, you can timebuild by flying "under the hood" with another airplane pilot, both acting as PIC and that cuts the costs tremendously.

Some places used to have Rotor Transition Programs, but many of the RTPs have been cut. I believe Mesa still has one. In a RTP, you enter an agreement with the company where they basically pay a training vendor your hiring bonus and you use that to get your airplane training and other requirements done.