I've wanted to do this trip since last year. This year the Alaska Railroad is offering the Spencer Glacier Whistle Stop trip 2 for the price of 1 for Alaska residents ($64 for 2 adults, unfortunately kids 2-11 are still $32 not 2 for 1). Oversize gear such as rafts incur an additional $20 charge (for all the items together not each separately).
The train leaves the Portage station at 1:25pm and arrives 20 minutes later at the Spencer Glacier. The train ride in is cool although a bit expensive for those of us just using it one way. But, it's the only way into the lake unless you have a buddy with a jetboat that can reach it. It took us about 15 minutes to offload the gear and strap the raft and frame onto a folding kayak cart (mine is similar to this http://www.rei.com/product/786433 ) Most everything else went in backpack style dry bags.
The hike from the tracks to the lake is 1.3 miles on a slightly uphill gravel path. I took us about 30 minutes with the gear and the kids. Once at the lake we started the raft inflation by using a 4 D cell battery air pump and the old fashioned hand pump method. By 3:30pm we were on the water floating past ice bergs. The glacier itself is about a mile across the lake and a mile back to the river outlet.