Pinned - means the barrel is pinned in place, look at your 28's frame and you will see a pin through the frame securing the barrel.
Recessed - Counterbored cylinders, i.e. the rim of the cartridge actually fits fliush with the rear of the cylinder face, the rims are surrounded or enclosed by the metal of the cylinder.
S&W introduced the 28-3 in 1982, eliminating the above features as a cost cutting measure, although there are appaerently some transitional 28-2's and 28-3 that share one or the other feature. The Highway Patrolman was discontinued in 1986, as they are not making any more of them and I think you can reasonably expect the value to continue to increase. Will it ever be as valuable or desireable as say a pre-war Registered Magnum - no, but more and more collectors are turning to higher condition 28's, and other less "desireable" classic Smiths as we are priced out of the market for the 27's, pre-27's, .38/44 HD's, etc. I'm probably not helping your dilemma any by being so long winded but you bought it for yourself, its a birthday gun, you should do whatever you want with it.