Newbie Here with Severe Emphysema and on Oxygen for the First Time

Hi,
Please excuse me if this is too long and if in the future I ask too many questions!
Four years ago I ended up in the hospital and never really understood why I was there for 5 days. I know that sounds ridiculous. I was on oxygen the entire time I was there and was given breathing treatments. I met with my GP after my hospital stay and all he could tell me was that I had COPD. I didn't know what kind. I have researched COPD to the enth degree except for emphysema. My grandfather had it and I was nothing like him. I totally disregarded it. I bought a pulse oximeter after getting out of the hospital and watched it go down over the 4 years. My GP never suggested that I see a pulmonologist. On my last visit with him I asked for a referral. I got it and it took 2 months to see him. I saw the pulmonologist last Monday and I he told me I have severe emphysema and he made all of the arrangements for 24 hr oxgen and mobile oxygen. I was dumbfounded. He wants me to be evaluated for a lung transplant. I was absolutely shocked and I still am. I've been on 24 oxgen since last Wednesday afternoon (29 Oct),
I have 2 questions:
1) Because my blood oxygen level was low before my diagnosis and now after having been on the 24 hour oxygen, can I run to the grocery store for just a few items without using my mobile oxygen? It seems like such a pain in the ass! The portable unit was explained to me but I'm not sure I retained it all.
2) Are there any tips anyone has for a newbie

Thank you very much,
Debbie in San Antonio, TX