92 johnson 40hp lower unit - rebuild advice

a 92 johnson 40 I recently acquired...I think the lower unit is in need of a rebuild, there is quite a bit of metal on magnetic drain screw. Rough estimate I got for rebuild is about $850 (close to double what I have in motor so far), not sure if that is inline or not? If so, will probably consider alternatives before I go that route, from attempting to do myself if at all feasible, or looking for a donor, or worse parting it out (gotta nice set of working controls i could sell thanks to Joe R help!).

Top end is good and was recently rebuilt as water got into VRO tank, runs very smooth. I was hoping to run the motor for this summer and address issue in off season, hoping lower doesn't shatter...but now second guessing and may moth ball her for now and keep my eyes peeled for donor for lower end.

Few questions: how difficult is a lower rebuild to do as a do it yourself project? Are special tools imperative, or can one improvise? I pulled gears and rebuilt lower on older 35 motor some time back and managed with a few pullers and a little improvising. If not feasible as a DIY, I will look for a donor as anti ventilation plate is in rough shape on this one as well, so putting 850 into a rough case seems silly.

Also, is it a total crap shoot on whether lower will make it through for 6 weeks, probably no more than 30 hrs of total run time? Is there any diagnostic to do short of opening her up to assess?

Did the magnet have fine shavings or chunks of metal ?

Thanks for inquiring...Mostly fine flat shavings, but there are some irregular shaped metal pieces mixed in like size of table salt, maybe slightly larger, and feels gritty when rubbed between finger/thumb. Not sure if that qualifies to what you would describe as chunks or not?

Racerone, any thoughts on this? Maybe I just run her till she blows and hope I've located a donor by then.