Hi my 150 special edition A Class Merc 2006 has problems,

yes a service overdue
when I stop and drive off it jurders then runs okay
but it runs slow, going up a hill it nearly stopped.
makes a noise in the engine area
going yo have my gearbox mended due to it leaking.
the garage says he'll fix the gearbox to see if it will run , but otherwise a write off.
now the word TRANSMISSION comes on the dash board.
Sometimes it rides okay but most times not , only use it to go to the garage.
It also shifts gears, only sometimes.
Need help, is it a write off?.