If you have tenure track position, your University should support your GC either in category of EB1 /outstanding researcher or NIW
You don't have to hire your own lawyer. The university has people to dealing with such cases. The difference is EB1 requires support from your institution but it is not necessary for NIW. If you have support from employer you will have much higher possibility to get GC approved. You can go for both OR and NIW with the support of University.