Broken dipstick removal on 1.8l Nissan Sentra.

remove the dipstick tube from the block/sump
they are either held in by a clamp and retaining bolt or are a tap in interference fit
use something like a pair of vice grips and tap out with a hammer

oil pumping out of the dipstick tube? you are getting pressure in the block from compression somewhere..bad rings usually cause this unless the pistons have issues..like tops burned through or broken by busted or stuck valves..

I gather from reading this that your dipstick has broken off and is still partway stuck in the tube and you cannot get it out or put a new one in? IF that is the problem, you can unhook the tube from the spot that it connects to the engine and slide the old stick out, put the tube back on and put the new dipstick back on it. There may be a bracket holding the tube in place that you have to loosen or remove. To remove the tube just pull it straight out.

the tube has a metal tab at the bottom of the tuabe with a hole that holds the tube to the engine with a bolt-remove the bolt, the tube will slide out of the engine, then you can remove the broken dipstick. For now, you might try to cover the hole at the top of the tube with a rag that you shove into the tube, leaving enough to grab when you need to remove it.

Hopefully, you still have the top part that is broken, take double sided tape and try that, if not the get a mechicanal finger and use that. Good Luck Tim