AOS (adjustment of status)

[Mcheries]

I'm an American citizen and I've had a long-time friend (about 8 years) who is a British citizen. He visited me in the U.S this year for our first meet, and I've gone to visit him in the U.K since. He just came down for another visit to the U.S and we decided that we want to get married and we did. He's still in the U.S with me and has only been here for 86 days. We spoke with a very good lawyer who said all we need to do is file for his adjustment of status to keep him in the U.S. The lawyer told us that it's an easy process and that if we want to hire him we could, but that honestly we could do it on our own just fine. I was wondering how I could start this process and had a few questions about it (that totally slipped my mind at the consultation with the lawyer). Would he be able to remain in the U.S after filing for his AOS or would he have to return to the U.K while we wait on the results of the AOS? Also if someone could tell me exactly what petitions we need to file for this, or have a step-by-step process that would be great. I've looked on the USCIS website and it's a little confusing. Everything I see on there basically points to an I-130 petition but wouldn't he have to return to the U.K for that?

Thanks.