Turnip
I would second MD600 Driver. You can easy get overhauled units from the USA which match the ones that were in there and just slide them in.
Otherwise your logic escapes me. Why buy an aircraft (I guess from an auction of the Bonus aircraft) which you should have paid bu##er all for, pay some avionics numpty to rip you off with all sorts of extras and things they didn't see when they quoted, and then end up with a 150 which is STILL worth bu##er all.
Bob