I'm betting a new pump is worth less than the time and materials to repair it. Fit a new one and give repairing that one a go just for practice of welding castings.
Its a D1102 engine...L series. Ive ordered a new one, but its been bodged in the past for at least 8 years. Initially thought it just a holed casting, that had been bodged up, was planning a Belzona repair, till I got it out.
Id say its do-able but new ones aren't that expensive. We replaced the water pump on our Kubota, don't remember exactly but think it was about £80 for a genuine part.
A new one is 68 quid shipped from the far east.....as for the local agent....waste of skin, about as helpful as a chocholate fireguard as its an old machine, they didnt sell. Guess where I wont be buying my new tractor.