I have the 1990 in PDF format and am able to print portions whenever I need 'em. I had one before, for my 86.5, but the pages got all smudged up, etc.
I am sure that there's a pre-89 version of the TRSM on PDF. That's what you need to get. Print off what you need, when you need it. I print mine off on 3-hole paper and place in a binder when I'm done, including notes that I write on certain pages.
Really no need to spend $80+ on a manual, unless you're keeping it for show and NOT using it. Using it will hose it up, just with BHG work.