Ya know, not everybody is chatty, and that's fine, but around here we usually at least say "Hello" and "Welcome" to new members and hope for a bit of introduction. So, Chad, "hello" and "welcome" to the forum.
If you get a chance and feel like letting us in on it, maybe tell us about where you are located, how you got into bikes, how you came to be an A10 owner, etc. No life story required or expected (but feel free tell as much as makes you happy). Then, pictures of your bike in all states of repair are always enjoyed. Oh, and don't forget to include your bank account number and mother's maiden name
Regarding your questions, if you haven't gotten the bike timed it may be a bit premature to worry about an oil pressure gauge. We have about 800 members on the forum and I would be surprised if 20 of them have oil pressure gauges.
I suppose you could set the timing when the bike is hot or cold, but cold is much more comfortable. You don't need to use a timing light to time the bike the way BSA intended owners to do it. You don't need to pull the mag from the bike. You do need to take off the right-side timing cover and loosen the magneto drive gear. You will eventually learn to tighten that gear in a way that doesn't change the timing you just worked so hard to set.
If, after reading the BSAwiki article, you still have questions, any number of folks here will be pleased to help (even physically in person, I'd venture, if you live close enough).
Richard L.