it often drops [ lower leaves ] when not having enough water, this one seems like it needs repotting. check the rootball if its too dry or too wet and check for any dead or rotting roots. Its a very old specimen and is probably rootbound. When it is rootbound it dries out rather quickly and because of poor drainage also suffer from occasional root fungus.

i recommend repotting it , regardless it does need a good mineral solution and a good fertilizer , i also recommend giving it a good amount of magnesium ( do not overdo it )

these pines a very pest resistent but sometimes when they get weak by under or over watering they can get infected. check for any aphids and mites ( tiny webs or red dots ) and mealy bug ( white plumes ).

this is a old specimen and to my opinion it is worth investing $ in.

How does one repot a tree of this size? Are there services that will do this? I am terrified of doing this myself!

Lol, I'm sure if we knew where you were...there might be people online that would help.
Every container gardener does this routinely.

For help repotting, you might try one of the better garden centers in your area.

well most plants can be grown indoors for a long time but alot of them aren't really permanent residents , eventually they get too large or they just become unsuitable for whatever reason.

the problem with using a pot that is neither small or big is that a plant still may become huge which makes it really difficult to repot. i always use big pots for bold specimen plants , for example i got a indoor banana which isn't too big because i got it in a really small pot, when im going to repot it im going to choose a very large tub - anything in between wouldn't be practical because it will still get huge and eventually gets too rootbound and i need to repot it again.

Choose a good looking pot, square or round. wide or long , contrast coloured or plain. Get a decent looking pot that you think will fit this plant and its enviroment.

repotting large specimen can be a pain in the ass, there is no way around it and it will make a mess. Alot of plants can be pruned to decrease size and weight and make repotting easier - this cannot be done with the norfolk pine, once you prune off and lower or middle branches they will not regrow or come back.

Remember eventually these kinds of trees will lose lower branches just like most mature trees, lower branches that do not receive enough light because the upper branches are casting shade. if one branch drops that not a problem but when multiple lower branches droop and drop it needs feeding , repotting and a fitting watering schedule.

one option of course would trying a garden center in you area or a professional horticulturalist.

Don't be afraid of repotting it yourself. It is a very durable plant.

Wow after seeing that plant it reminded me of Cousin It from The Adams Family. It needs more light. Obviously the plant was just coasting along with the last residence. A tree that size shouldn't droop like that. Get a bigger pot and transplant!