not that hard
great game and not that hard you can beat it in under 40 jumps easy. the main problem is lack of instructions and knowing what to do. some things i found useful that weren't covered in the instructions
(1) go for perfect jumps - if you get in your trolley at the right time and take off at the right time you get a 1000 bonus points plus double trick points.
(2) before you can afford tricks do 360s each jump this gets you 360 bonus points each jump - it's just doable before you get the first rocket thruster but easy as pie after that
(3) proceed to get max wheels and thrusters, and get the propeller hat, the bat, and full groupies. and hit the space shuttle you get bonus points
(4) save up for the handstand air trick first and polevault ground trick second, ignore the other tricks.. doing combos with these you can easily average 30-50,000 points per jump
(5) don't buy the dumpster until you can also afford the dumpster rocket, same deal with the gold trolley and hang glider, they're not worth it otherwise
(6) to get underground to fight the worm do a dumpster dive and continue holding the down key
(7) to fight the worm and monkey always have a full load of groupies they act as human shields (stick figure shields?) and protect you from bombs, and at this stage of the game you can afford groupies easily