Reddit mentions of Fieldwork Is Not What It Used to Be: Learning Anthropology's Method in a Time of Transition

I agree with /u/keyilan that its not too late to go back to school in your 30s. I started my PhD at 33. I have a friend who started her MA (and is now in a PhD program) in her 50s. That being said, if you have a stable job you're happy with and want to avoid going into debt, and if you're not completely and totally sure you want to pursue a degree in anthropology, then it's probably better to be an autodidact.

Anyway, here's some suggestions for some stuff on sociocultural anthropology methodology (and historical descriptions of such things) that may be of interest to you.

Research Methods in Anthropology: Qualitative and Quantitative Approaches by H. Russel Bernard (he is the methods guy in sociocultural anthro--and this book is rather dry but super detailed and will teach you all the basics of anthro methodology.)

Decolonizing Methodologies: Research and Indigenous Peoples by Linda Tuhiwai Smith (a classic text in indigenous methods.)

Participant Observation and The Ethnographic Interview by James Spradley

Fieldwork Is Not What It Used To Be edited by James Faubion and George Marcus (I have not read this, but have heard good things about it.)

Before Boas: The Genesis of Ethnography and Ethnology in the German Enlightenment by Han Vermeulen (this is a history of ethnographic methods rather than a book about methodology, but it's super interesting.)