Hi kingsfoil:
I know exactly the feelings you are having for a vehicle you have owned and loved for years. I had the same feelings for my 2013 E350 Econoline Van w/ 224K miles on it that I bought new, always garaged and had just put 4 new, $1300 Michelins on. I got a check engine light and 2 days later a little wrench showed up on the dash. Everything still seemed just fine. Ran fine, shifted fine and all was good so the shop cleared the codes and I went on my way. Two weeks later the same ck engine & wrench came back. The shop did a diagnosis on the code and said I needed a new HD, 5 speed trans overhaul for $6600.00. (this trans was behind a V10 engine) Another trans shop said exactly the same thing but quoted $7150.00. I bit the loss bullet and sold it for $5000 as-is. The van was worth $6500-$7200 on KBB so if I put the trans in it for $6600 and sold it for $6500, basically, I gave it away. Bought a new Transit T350 and very happy I did because when I sold the E350 and was looking through my folder, I found that I had spent $3200 in the past 2 years on many, many small things (but they add up!). That E350 was $300 - $500 dollar-ing me to death for the past 2 years.
So, my advice to you is to sell it and move up to a newer one with 1/3 the miles and move into the current generations of Expys. If you just love it no-matter what, spend the money and fix it but I am thinking that in the future that you will REGRET that decision. Just my 2 cents worth of thoughts from experience, for whatever that's worth? Lance (Picture attached of 2013 E350 in 2017 [RH fender bender] - Still looked exactly like this the day I sold it)