In need of advice

[Saga Lout]

Hello fellow Scoobie owners.  I have a 1999 (Reg'd March 1st, 2000) Legacy Estate - wrongly described in teh log sheet as an Outback but it isn't.  That's academic really but my problem is this.  My car started out as having pneumatic suspension but for some reason, a previous owner turned the front suspension off and replaced it with coil springs.  The rear end seems to have sugffered from that and it's never very long between top ups.  I have to go to a garage for that because filling stations' airlines only put up around 80psi and the top up I need is at least 110.  I know I could buy a compressor but I'd like to know roughly how much it would cost and how to do it to and bring it back to the way it was when it left the Fuji works.

From what I can see under the bonnet, there aren't too many parts to source and put back in but what problems would I encounter if I tried to replace it? A year ago, I should have done this when the engine was away being rebuilt after a sieze up but I was too busy making enough to pay for that fix.

All suggestions welcome and thanks in anticipation. 

[Saga Lout]

Forget it.  I'll get me coat.