Hi Paul,
It depends if it's ghosted and how dirty it is inside, if it doesn't smell then just use a bottle brush to remove any carbon build up, bend the brush to get it round the kneck of the gourd but be as gentle as you can.
If it's ghosted you can use high strength vodka to clean it, simply place the gourd in a bowl with a tea towel in (to stabalise it & keep it upright) then pour the vodka in the gourd at the wide end. Use enough that it comes to about a cm under the cork, warm the vodka if you can as I've found this helps. Move the calabash in a circular brandy snifta motion to help agitate the gunk but be very gentle and very careful not to get vodka on the cork ring.
A good tip is to rub some Vaseline on the cork before you pour in the vodka which I've found helps protect the cork during this process.
Then leave the vodka to sit (about 20 minutes is good) and you pour the dirty vodka out through the THIN STEM END (VERY IMPORTANT!) and the liquid that comes out will probably be brown. You then leave the gourd to dry for a week and see how it is (it will probably have a slight vodka smell but that goes after a couple of smokes) if it is ok you can then smoke it if not rince and repeat.
For long term care of the cork ring I use cork grease that is used for musical instruments (you can get it on Amazon it's shaped like a little lipstick), it smells but after a day or two that completely dissipates. You simply run the little stick round the cork ring then leave it overnight and the next day take off any excess and rub/work the rest in, this will help keep the cork supple and nourished.
As for the meerschaum I use high strength vodka and a cotton wool earbud but you MUSTN'T do that if the meerschaum is pressed which I think yours might be as it looks like a Pioneer Calabash and I believe they used pressed meerschaum. I don't have any experience with pressed meerschaum cleaning but I'm sure if you look on the forum the information will be there.
For maintenence of the meerschaum bowl you want to keep the cake as non existent as possible and the best way is to wipe the bowl with a piece of tissue paper after each smoke once its cooled.
As for the mortise I'd say it should just screw in and wouldn't need glueing, I have one which is similar and that just screws in. My advice would be to try and if it screws in firmly then you're good to go.
After smoking detatch the meerschaum bowl and leave the gourd so the air gets in and it can dry out.
That just about covers everything I can think of and I hope it helps.
Chris.