a lot of it depends on the religion Nae. perhaps if you mention what religion (and add to the title) people will be able to help more. a catholic baptism (for instance) is significantly different to the dedications as some churches...

thank you gifts for guests aren't needed. some cultures (greek orthodox for instance) have gifts - but it really does come down to cultural choice

we had a biggish deal for DD - but after all we'd been through to get her here (which i'm sure you appreciate!) we used her baptism as a way of introducing her to a large number of people all at once, and celebrating her arrival. we had it as a stand alone service - mostly to fit in with people travelling here for a birthday the next day - the Priest was happy to do it on our time and at our local church (next door!) to accommodate this, although most baptism occur as part of the normal sat night/sun morning service at the main church (c'hill)

generally you have a meeting with someone from the church to ensure they have the details correct (baby, parents, god parents), and you may be asked to attend a normal service in the weeks leading up tot he christening to introduce your bubba to the church community if you're not already going to church regularly (this is what happened with us - as catholics - not sure about other religions)