Try XRDP. It doesn't have all the features MS RDP has but the features it has work well. You can use different rdp clients like mstsc, rdesktop, freerdp and thin clients. http://www.xrdp.org/

Here is something that may help you. Note that this will get you the public IPs directly to the WAN interfaces and requires bridged mode on the CPE: http://blog.angulosolido.pt/2008/03/intelligent-linux-gateway-multihoming_04.html There is also a (warning) very bad video about it: http://blog.angulosolido.pt/2008/03/intelligent-linux-gateway-bad-video.html

Short answer: Yes

Long answer: It has been done by many even with Open Office 2.x. As long as you don't need MS Access shouldn't be a problem. 90% of Ms Office users use up to 10% of the available features. Even OO is overkill for many of them.
Advice:

- show confidence on the project
- provide excellent support during the migration
- quickly solve any existing issues that may appear
- leave a (legal) copy of Office 2003 installed on a Virtual Machine for the unlikely rare situations