Much as I understand the feeling, and feel for you (and your credit card/s ... ), one has to be grateful that the car has run for 250K Kms without needing much by way of repairs. Many cars are scrap heap material by 150K Kms, even these days!
After this 'repair cycle' is completed, it should give you many more years of (relatively) trouble-free driving. Just think of it as a 'major overhaul' ...
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Similarly to your situation, I could see a whole lot of repairs coming over the horizon for Roo1 (236K Kms), biggest of which was the gearbox - nearly 18 years of driving it like I stole it couldn't possibly have contributed to this, could it? If it had suited my needs, I would have done the required (foreseeable) repairs, and kept it forever. Which is one reason why I turned it over for Roo2.
Roo2 has cost a bit in maintenance and repairs (new tyres; 125K Kms service; new non-SLS struts at the rear; spare chipped key; sheep seat covers), but it is really a far more suitable vehicle for my uses than the Impreza ever was. The Impreza was much more economical around town (around 10L/100 kms even in stop-start traffic with the air-con on), but Roo2 is better for my uses in every other respect. Still far cheaper than what needed doing to Roo1, and the vehicle suits me better. I'm happy.
As for the leaky head gaskets problem, our neighbour across the road needs to have them done on her 2004 SG series I at 125K Kms. It's going to cost her around $4,000
. It is my understanding that the series II SG uses the newer, non-leaky design gaskets as standard. Hopefully that's the case! What with the EJ-253 heads being a completely different design from those on the EJ-251, I would hope that Subaru have fixed that particular problem.
Did you get a better price on your steering rack repair?