rockers/valvetrain + oil = mess?

[tab a]

I replaced a broken rocker arm on my '72 350. Read through a number of old threads on adjusting valves, some of which said that doing it with engine running was really messy. How much oil should be flying around?
I really didn't have much, and wondered if this is suspicious for a lubrication problem? Engine was not really warmed up, and oil pressure was about 25#.

2. Did 350's of that vintage all have hydraulic lifters? If not, how would I know which I have?

Thanks!