Seefutlung, I understand, you do have film and digital experience but the world of film photography has changed considerably since the days of film. If money is a concern, the matter of paying now with a swift swipe of a sword across the midsection with digital or paying later with the death of a thousand cuts every time you purchase and develop film, is flawed as it pertains to this particular situation. urufan56 stated that he would like to shoot nature photography and portrait photography with a rugged camera system at or around $300.
Jumping ship from the Canon FD mount to the Canon EF mount in addition to the new body he already seeks is the glass, Now for wildlife, on a crop body digital he is looking at something in the aria of 200mm and for portrait stuff something around 50 to 100mm. A 70-200 would suffice for that, however should he stick to a film body that 70-200 will not work to satisfaction for wildlife, (trust me I tried, was very unhappy). You are looking at a minimum of 300mm. One would be hard pressed to find a 70-200 alone for under $300 let alone the big glass, requiring a long wait period before one of the desired photographic interests is in reach because he still has to get the body first. This brings up durability, I take good care of my cameras but despite that I firmly believe that no consumer level digital SLR would stand up to what I have put my my geat through in the field shooting wild life. Ice, snow, rocks, trees, water it has seen it all, For that kind of wether sealing and shock resistance you are looking at upper mid to high level bodies or additional covers. Switching to digital here one is sacrificing some of the the durability they are looking for. I'm not saying that consumer level cameras can't do it but one will miss shots worrying about how the camera will hold up or wile waiting for repairs. What I am saying is $300 is not going to get what is needed to suit the goals of the OP with modern equipment in one quick slash.
Yeah, It's just why spend money on lens that you can't use later in life and you have grown accustomed too? I just want to open up the possibilities if I did get the film camera and not like it, and I already had my lens, I could use my lens on a digital camera. I you see what I mean.
Well, Two things, the price tags of film equipment is at rock bottom, For the most part you can buy it and use it for some time and unless you screw it up you can sell it again at or near what you paid for it when you move on. Also there is the ever pressent crop bodies, The crop body cuts away part of the frame as it would have been on film effectivly altering the percieved focal leingh of the lens. It will be like getting a whole new lens even if the lens you have grown accustom to is compatable to the digital camera you upgrade to, it will not behave the same way it did on your full frame film body unless you get a full frame digital, but I think the asking price for those is ones first born son. You could find them used for around a grand I think, but that is beside the point.
Additionally, FD-EF Adapters are made, not the most common peice and not perfect but they are available.
In the end the decision as to whether you switch from FD to EF is yours to make, I'm just trying to keep the possibilities as open as I possibly can.