Earlier last year the headliner near the windshield was coming apart and was easy to reglue. Now above the drivers head leading to the driver's window and somewhat back from there the headliner is drooping. This is more involved so I might just go to an upholsterer to do the work to make it look good.
is a upholster the appropriate people to do this work?

Yes. It can be done diy. But I’d watch a lot of YouTube first

I’ve done several headliners. Easy. Watch YouTube to get the technique.

Hardest part of the job is getting the A and C pillar panels off without breaking the clips.

It's definitely something you can do yourself. If you're not feeling it, though, call around to local upholstery shops and see what they charge to do it. I had one shop quote me less than 200 all in on a headliner for an r53, and honestly, it was worth it to me just to drop it off in the afternoon and pick it up looking brand new and perfect the next morning.

Interesting the first two vids. I watched didn't mention the A & C pillars.

Will think about it, whether to do it myself or farm it out. The A&C pillars give me pause.

I have the same problem on my '06. I plan on removing the headliner myself, and having a local upholsterers re-cover the headliner. From their reviews and word-of-mouth, they have an excellent reputation for their quality of workmanship. I'm going to take this opportunity to change the colour from the original light colour to something along the lines of Anthracite.

In the videos that you watched, how did they get the headliner out from behind the pillars?

I did two Gen 1s last month and both required all the trim removed.

We got the A&C pillars off without breaking the clips. It can be done, you just need a variety of tools. A cotter pin tool worked the best.

This is the vid. that shows the pillars in place. Someone asked about removing the pillars and he said you don't need to - just flex out. Same thing with the rear rubber seal - he left it in place. This makes it much easier and less chance of breaking a clip.
Where did you purchase the original headliner fabric?

You Tube

You Tube

We did the headliner restore back in 2018 using material from yourautotrim.com. Went for an OEM light gray and it matched 90%, close enough!

What I ordered: Auto Headliner "Lt. Grey" PH-2075

A-pillars come off fairly easily, B-pillars (belts) come easily, rear C pillars did not detach fully so I just pulled them down gently and had the kid help me wiggle the headliner out and away from the covers.

This was easy compared to the Cayenne I just completed. The MINI is tiny and much more manageable in size! Definitely doable.

I have never had to dd a headliner before, even my '68 Charger that I owned until 2008.
I hope I don't have an issue with the Macan.

Had a local upholsterer do mine (it was a little hole in the wall place in Oxnard). Guy did it in 1.5hrs for $200 looks fantastic, guy definitely knew what he was doing.

I have a 04 R53.
I re-did my headliner myself about 6 months ago. I haven't had much success or confidence with shops working on my Mini in the past. I prefer to do the work myself. I did some youtube research as well.
Everything went well with removing all the interior hardware except for the immobilizer. The clips holding the cover in place were so brittle; they all broke in multiple pieces.
I did not have to (or even tried) remove any of the pillars. I find - you don't have to ( besides; I don't like messing with anything containing an airbag).
I have dual sunroofs. After peeling back the rear seal around the back hatch - The whole headliner just slid out with a little, gentle bending and maneuvering away from the sides. Cleaning the old foam from the headliner is easy but messy, indeed.
I managed to source some nice comparable (color and better quality) fabric from Jo Anne fabrics. Be sure to use a good quality high temp spray adhesive. Work clean. Don't skimp - spray the adhesive in a uniform cross hatch pattern. Take your time.
Start to finish R&R - about 6-7 hours. total cost = $35.
My headliner turned out perfect.

Go for it!