After two years of being in a wheelchair, Andy's leg muscles would have atrophied to the point of him not being able to walk or even stand at all.
The church the wedding takes place in appears to be Catholic, given the later confession scene and the use of a rosary, but Catholic marriages that take place in a Catholic church don't happen in a hurry, as Keith mentions theirs did-there are required preparations that take time, and if both parties are not Catholic, there may be issues regarding the use of the sanctuary. You can't just reserve a date and get married, in a Catholic church.
At 44:20 into the film Christine us driving her Jeep to a Nursery. As her Jeep comes to a stop you can clearly see that one of the break lights (left side) is not functioning.