Think of it this way:
1) Are you willing to put up with a horn that´ll look like an amateur fiddled with it?
(It WILL look like that. I´ve seen a tuba with a leadpipe WELDED to the bell. It had been taken to a mechanic PROFESSIONALLY doing dentwork on cars. Don´t know the English term).
2) If so, what do you think is the value of one hour of both yours and your Dad´s spare time ?
3) How long do you estimate will it take to get all parts / tools / material in place, and then do the work twice b/c you´ll probably mess up the first time (at least)?
4) By what percentage do you guess the repairperson will raise their fee when you eventually let them fix what you messed up, just to let you suffer for it ?
Take all these factors into account and see what you get.
By the way, I don´t know the shop you took that horn to, but from what you described I wouldn´t let them touch my instruments. They recommended to GLUE parts on the horn




