I think they may be right.
I bought a 89 S 10 with 2.8.
But it had just a new engine put in it. At about 40,000 miles. the guy said his kid ruined the engine and that is why he is selling it. after he put the new eng in it.
I think the prob was the port in the heads that let oil drain back to the crankcase was too small. And this caused a lot of failures.
The new eng that was put in had those ports enlarged.
I drove the that blazer another 140,000 miles.mostly highway miles.
However, $2800 is tooooo much money for that s 10.
last year i bought a 1998 S-10 blazer, in great shape, loaded with everything and everything working, factory tow package,, with the 4.3 vortec engine (standard)
with 129,000 miles on it for $3,200. and that was the average selling price not a special deal.
Your 92 would would be worth about $1500 -1800 if it was a blazer,, if it is a pick up they sell for less.
Google "edmonds cars " and see what they say the truck is worth.
Aso, look on "craigslist" to see more S 10 for sale.
My 98 is a way better s 10 than the 92 was in everyway, except the 2.8 got better mpg.