The LK 3054 does have a shuttle. To try to answer your question about "shifting on the go"... the answer is yes and no. By no stretch of the imanagation, could you call it equal to the DK series as far as ease of shifting on the go. Might I sugest that it will require a higher degree of operator skill. It can be shifted up a lot easer than shifting down.
The price you quoted is not a real steal. If the machine is in pristeen condition. Check the oil filter to see if it is a Factory one or if it has been changed. AT 100 HRS, THE ENGINE OIL SHOULD HAVE BEEN CHANGED TWICE, THE TRANSMISSION ONCE. If it has not been changed at all ... then that will tell you something. Look at all the grease points. If it has been greased then it will be evedent. If it has not, it will also be very evedent. Have all implimants been well mantaned or not used at all. Has the machine been out in the sun / snow /sleet/rain/etc. all this time?
The LK 3054 and 3504 was my bread and butter for many years untill the DK came in. The LK is a good, stout, no frills machine.
To help you nail down the value of this used machine... I can get you into NEW LK3054XS, 6 foot tiller, 5 foot finish mower, and 5 foot box blade for about seventeen grand.
If this used machine is on a deelers lot - then he may have some room to play with. If it belongs to an indivudual, then many other factors will come into play on the selling price. such as: Did the owner "soak it to the guild" as far as financing, or did he do it right? Why is he getting rid of this machine? Does he need a differant size, is he moving into a highrise in downtown New York City and dont need it any more? I just stole a ford 1320 (600 hrs and WELL mantaned, garaged) /loader/ NEW Woods land plane/ BARLEY USED woods mower with chains, Quick Hitch/ / and 7 foot rake with guage wheels. The gentleman needed some money NOW for a triple by - pass.
There are some real deals out there. You, Sir may be paying top dollar for this machine. Its worth this price, but no more.