How do you remove the last two nuts or bolts located under the bell housing on a 1999 chevy astro van

Are you referring to the oil filter? It is located under the engine on the drivers side just in front of the flywheel cover on the transmission. The drain plug is a 15mm bolt.

You'll need Hydraulic Floor Jack, Jack Stands, Wrench Set, Socket Set with extensions, Screwdrivers, Pliers, HAmemr, Pry bar, Fluid Drain Pan, Light, Rags, Containers to organize nuts and bolts, and possibly an assistant to help you out.
Then follow these steps:
1. Disconnect the negative battery cable
2. remove the black plastic air intake to create some room
3. Remove the transmission fluid dipstick and if possible the dipstick tube
4. Remove all brackets, hoses or cables that connect the engine and transmission
5. Locate starter motor and remove easily accessible starter bolts
6. Remove any of the top bell housing to accessible engine bolts
7. Chock rear wheel to raise the front of the vehicle
8. Drain all transmission fluid
9. Put the oil pan back in its position but only tighten the nuts by hand
10. Remove the driveshaft by removing the 4 U-joint bolts that hold the driveshaft to the rear differential
11. Disconnect all electrical connectors and hoses
12. Detach the oil cooler liens of the transmission
13. Remove the starter bolts
14. Remove the torque converter for the flywheel bolts
15. Remove all the bolts and nuts that are holding back the transmission mount
16. Remove the cross member
17. Remove the exhaust crossover pipe
18. Remove the transmission bell housing bolts
19. Now remove transmission from the engine and bring it down to the floor by removing the remaining bell housing bolts.
20. Lastly, remove the torque converter from the transmission
To know more in detail, please refer to this video: https://www.youtube.com/watch?v=t7PVog9gD2o

You'll need to remove the interior engine cover(dog house).Torx screws for the covers, 2 bolts on floor. and bolts against the fire wall (i use a long extension with a swivel socket at the end). The IAC valve is screwed in to the side of the throttle housing (where the gas pedal hooks up to the engine).I can get a pic if you need it.

Under your van on the passenger side just above the oil pan on the side of the engine block, bolts into the transmission bell housing, hope this was very helpful.

It is the same transmission but the 99 has a different bolt pattern. If the 1998 has a removable bell housing(it could be either way) You will have to switch the bell housings. The bell housing on the 99 is removable. If they both have removable bells then it will work.

should be a rubber plug on the end of the door

To replace the power window motor:

1. Remove inside door panel, and locate the motor.

2 Unplug the motor, drill out the rivets that hold it in, then you can remove it.

3. the new motor may come with fasteners to install it, otherwise use 1/4 - 20 nuts and bolts to attach the new motor.

this is an older rear wheel drive car you don't need to remove motor, i would along with these instructions get a repair manual (Haynes) for reference purposes, jack up the front of the car , support on frame with jack stands, remove battery cables, remove starter, all electrical plugs on tranny, then remove access panel for torque converter bolts located at lower front of bell housing, after access plate removal rotate torque converter to the point where you can not only unscrew converter bolts but also remove drain plug to drain converter. To stop converter from turning during removal of nuts you must lodge a large screwdriver between the flywheel gear teeth and the engine block at an appropriate location ( at starter location usually) after removing all torque convert.nuts jack up slightly or support trans with trolley jack and 1 ft length of wood under pan, proceed to remove all bell housing bolts except for the top one, remove that one last after removing the drive shaft of course, also make sure you remove the transmission crossmember after jacking up trans slightly. the idea is to allow the tranny to only be attached at the end of removal by the one top bell housing bolt and supported by the trolly jack and two bye four or better 3/4 in thick 1 ft X 1ft plywood board after unscrewing the last bolt the trans. can be pulled back away from the motor and lowered down. the installation is reversal but aligning the torque converter to engine can be problematic sometimes (patience and strength) you can do it!

try a stud remover.

There are two bolts that have to be removed from under the hood with a LONG extension or sometimes a long heavy duty screwdriver.They are located towards the top of the doghouse & quite a ways back in.Good luck,
ChevRev