Hi guys, looking for a little general guidance - any comments would be real helpful.

Our (not .NET-based) development team is working on a project to export data in XML to a (.NET-based) third-party system.

At the start of the project we were asked to provide an XML schema (.xsd) file describing our export data to a contracted-out development team so they could develop an import routine for the .NET-based system. The file format is quite straightforward and contains approx 500 attributes.

The problem is, to be honest, we didn't do a great job on the initial XML schema so we need to revisit it. The changes we need to make are:
- approx 75 attributes have incorrect maxLen values and need to be extended.
- approx 20 attributes have the wrong data type.
- approx 20 attributes need to be renamed.

We've done the work in our system and produced an updated XML schema file that now contains the correct values.

But now we need someone to apply these changes in a .NET environment and we have little .NET development knowledge in-house - so estimating how long it will take and how much it will cost us is kinda tricky. I guess this is like asking 'how long is a piece of string ?'; but if anyone with experience of this sort of change could offer any guidance (hours? days? weeks?) we'd really appreciate it.