As sabre said, 4100' is going to require a straight-wing Citation if you want to go anywhere of distance down the road...and with your budget you're looking at a C-II or S/II.

$1M to overhaul the JT15D-4 is highway robbery...with a consultant such as EMS you should be in 700k range, maybe a hair less, out the door.

The Citation II handles icing just fine...everybody hates on boots but they work GREAT and you don't have a hot wing robbing power when you're not accumulating ice. The bleed air windshield heat is the worst part of the sytem IMO and fogging is fairly common if descending from high altitude into a warm, humid destination.

The C-II also does well with 0.4" of clear ice from FZRA all over the airplane...ask me how I know <scared>