Volvo: 1989 240DL wagon, haynes repair manual, nox 2

Question
Hello, I've reached a crossroads with my Volvo.I've been restoring her and have gotten her re- registered, insured and she has passed all safety inspection tests. She has failed Emissions.
Readings: HC 0.91 gpm  CO 10.29 gpm  NOx 7.85 gpm            Limits:   HC 0.80      CO 15.00      NOx 2.00
So Far I've done all the work myself and have spent around  900.00, which is probably more than she's worth. She has 148,000 miles, virtually no body rust(unusual),brand new cooper radials,brand new battery, a few body dents and scratches. I want to sell this car, not for a profit, in fact I realise I probably won't make back my 900.00, but she still has many miles left in her and someone should be able to use her. I can't stand the thought of her just going to a yard, so the question is:
Should I try to replace the Catalytic converter and/or oxygen sensor to get her to pass emissions, or try to list her as is? Friends and family are telling me to donate her and take the tax write-off.Meanwhile I'm continuing to pay insurance. I believe I have enough ability to replace a Cat. and sensor myself, as long as there is no welding involved. I don't have a lift, but I have ramps so I could put the front or back up on the ramps. The Haynes repair manual does not offer much help for these two procedures, in fact I can't even find a picture of the Cat. in there. I've seen some listings for a Cat. on e-bay, but am not quite sure of which size to order, and again, the manual is not helpful. I think it's the 2 inch version, this car has the 2.4 Jetronic engine. Your expert feedback will be greatly appreciated.
many thanks indeed,
Mark

Answer
My biased opinion says you should keep your car on the road for a few reasons.  You're probably right that you wouldn't make back the money if you sold it, especially after failing emissions.  However, consider that even with these repairs, the money you're saving on insurance and car payments probably offsets that a lot, assuming you would own a newer, more taxable car.  Once it passes smog, there's no reason to believe it won't be as, or even more reliable than any other new car on the road.  I've invested in my car much more than I could ever sell it for, and consider my ownership a complete monetary loss.  Given that, I've decided to keep her on the road as long as possible, knowing that in the long run I've saved a lot of money in insurance and no car payments.  I would say go for the cat repair.

The job isn't too bad in my opinion, and you can get cats for less than 100.  As for how the procedure should be done, there are various opinions, so to be fair to the subject, I'm going to recommend you visit www.brickboard.com, a free volvo forum where you can post questions and get opinions and responses from fellow experienced 240 owners.  You should get quite a few detailed descriptions of how others did the job you're currently facing.  Good luck!